GIS
Maricopa County AZ GIS provides public access to county mapping, aerial imagery, parcel information, geographic datasets, survey information, planning maps, transportation data, flood information, and other location-based records. This article explains how the county GIS program is organized, which official mapping system fits different types of searches, how to work with parcel and geographic data, what information to prepare before searching, and what limitations users should keep in mind before relying on a map or downloaded dataset.
County GIS Services
Maricopa County's Geographical Information System provides mapping, imagery, and geographic analysis services for county residents and government agencies. The county maintains a central Geographical Information System page that serves as a starting point for public GIS information, mapping requests, and related county services.
GIS is not a single map containing every county record. Maricopa County operates multiple specialized applications because different departments maintain different types of information. A resident researching a parcel, for example, may need the Assessor's Parcel Viewer, while someone looking for zoning information may need a planning application. Surveyors may need land survey points, and residents researching flood conditions may need a Flood Control District application.
This division matters because the map that displays a feature is not necessarily the department responsible for the underlying record. GIS technology provides the geographic interface, while property, transportation, planning, election, environmental, and flood information may originate with the county department responsible for that subject.
Choosing the Right Map
The county's GIS Mapping Applications directory organizes public mapping applications by subject. Reviewing this directory before opening individual maps can save time because it identifies applications designed for specific searches rather than forcing users to locate information through a general map.
General Mapping Applications
General GIS applications cover several of the most common public searches. Available applications identified by Maricopa County include:
Parcels, for viewing parcel information.
Overdue Property Taxes, for parcels with overdue property taxes and unsold liens.
Historical Aerials, for aerial imagery from different years.
Planning and Zoning, through the PlanNet mapping system.
Survey Points, for county land survey data.
Where to Vote, for locating voting locations based on an entered address.
Parks, Trails and Amenities, for county-managed recreation locations.
No Fence Districts, for determining whether a property falls within a designated district.
Lake Pleasant Water Levels, for viewing the shoreline at different water levels.
Waste and Recycling Facilities, for locating county-related waste and recycling facilities.
Elections District mapping.
These applications serve different purposes even when they display some of the same geographic features. Parcel boundaries may appear in multiple systems, for example, but that does not make each application an authoritative source for every property-related question.
Flood Mapping Applications
Maricopa County also provides GIS applications focused on flooding and drainage. The mapping directory includes an application for effective FEMA 100-year floodplains and elevation certificates, rainfall and weather data from the Flood Control District, flood project mapping, Lower Gila River floodplain updates, and the FLO-2D Web Access Tool.
The FLO-2D application allows client agencies, consulting engineers, and members of the public to access two-dimensional model results from Flood Control District ADMS(P) projects. The county states that technical information within the system may be viewed, downloaded, and printed.
Users should distinguish a mapped flood feature from other property records. A parcel map, planning map, and flood map can show the same location while answering very different questions. Selecting the system that corresponds to the underlying subject is the safer approach than assuming that one map contains every applicable condition.
Transportation Mapping
Transportation GIS applications include the Road Information Tool, road closure mapping, Adopt a Road information, the Transportation System Plan 2035 Phase II, and the Active Transportation Plan. The Road Information Tool focuses on roads maintained by the Maricopa County Department of Transportation. The Active Transportation Plan map also allows residents to select a location, submit a comment, view approved comments, and reply to them.
This distinction can be useful when a road appears on a map but the user's question concerns maintenance responsibility, closure information, or a transportation planning project. The transportation-oriented applications are designed around those specific county functions.
Environmental Maps
Environmental GIS applications cover mosquito management, environmental health plan review districts, restaurant inspection ratings, air quality, air quality facilities, and Environmental Health office districts. Because these applications connect geographic locations with specialized environmental or regulatory information, users should select the application that matches the subject they are researching rather than relying on a general parcel layer alone.
Parcel Viewer Searches
Property-related searches are among the most common uses of Maricopa County GIS. The official Assessor's Parcel Viewer provides an interactive map maintained through the Maricopa County Assessor's Office and county GIS infrastructure.
The Parcel Viewer supports searches by parcel information and map-based selections. One search option accepts a Parcel Number, also called an APN. The application shows examples in formats such as 13275013 or 132-75-013. Preparing the APN before opening the viewer can make a property search more direct because it identifies the parcel more precisely than visually searching a large area.
Parcel Viewer Features
The application includes several tools for working with map information. Users can turn layers on and off, select map features, view feature information, draw on the map, measure distances or areas, identify coordinates, change basemaps, create spatial bookmarks, print the current map, and search using entered information or shapes drawn on the map.
The Parcel Viewer also allows map selections involving parcels and provides buffering tools for identifying features within a specified distance. Search results are limited to 1,000 records, so broad searches may need to be narrowed when a selection covers a large area.
If the search box or parcel details do not appear correctly, the Parcel Viewer specifically advises users to clear their browser cache. The application also states that Internet Explorer is not supported and recommends a current version of Edge, Google Chrome, or Firefox.
Parcel Boundary Limitations
The Assessor's Parcel Viewer contains significant limitations that users should understand before relying on a displayed boundary. The Assessor states that information in the dataset or map is used to identify, classify, and value real and personal property, but the information is not guaranteed to be accurate, complete, or current.
The map is also not updated in real time. Information may have been gathered from independent sources, and errors or omissions may have occurred while information was collected, interpreted, or reported.
Most importantly, parcel boundaries displayed in the map are described as illustrative. The way adjacent parcels appear in the viewer may not always be consistent with recorded documents. The county specifically states that the map is not the equivalent of a title report or real estate survey. Users should independently research and verify information before relying on it, particularly when preparing documents or making decisions that depend on exact property boundaries.
GIS Open Data Portal
People who need geographic data rather than an interactive map can use the county's GIS Open Data Portal. The portal allows users to search for and download Maricopa County GIS data. Available subject areas include parcels and property data, elections, conservation, Flood Control District information, natural environment data, and other county datasets.
The county states that many datasets are updated at least daily, while others follow weekly or monthly update schedules. This means users should not assume that every dataset reflects changes at the same time. A dataset's update frequency can matter when a project depends on recently changed property, infrastructure, boundary, or environmental information.
Downloading County GIS Data
The Open Data Portal is intended as a self-service source for GIS information. County material describing the portal states that users can search, preview, and download available data without submitting a data request form. Available data may include boundaries, aerial imagery, zoning layers, environmental overlays, and other geographic datasets.
Before downloading or using county GIS data, users should review the portal's terms and disclaimer. Maricopa County does not guarantee the accuracy, completeness, timeliness, or correct sequencing of the information. The county places responsibility on the viewer or user to verify accuracy before accepting or relying on a dataset.
Distribution and Commercial Restrictions
The GIS Open Data Portal includes restrictions on distribution and commercial use. The county states that external distribution or use requires contacting the GIS office for written authorization. Unauthorized distribution or use may violate county policies and state law.
The portal also states that downloads for commercial intent or resale are prohibited except in accordance with a sublicensing agreement. Users planning to redistribute, sell, publish, or incorporate county data into a commercial product should therefore review the applicable county conditions rather than assuming that public download access automatically permits unrestricted reuse.
County GIS Data Requests
Not every geographic dataset is handled through the same process. Maricopa County's GIS data request information separates products by the department that maintains or distributes them.
Assessor Property Data
The Assessor's Office provides geographic and property-related datasets that support mapping, property research, and land records management. The referenced products include parcel boundaries, subdivision outlines, assessor book boundaries, ownership records, address points, and property characteristics such as square footage, year built, and land use.
Before requesting Assessor data products, the county directs users to review the Assessor's Office Parcel Data Sales Policy. The policy covers procedures, licensing terms, costs, acceptable uses, redistribution limitations, and any attribution or citation requirements that apply when information is shared or published.
This distinction is useful because downloading a public GIS layer through the Open Data Portal and obtaining an Assessor data product are not necessarily the same process. Users looking for a particular property dataset should first determine whether the information is already available through open data or is an Assessor product governed by a separate policy.
Flood and Transportation Data
The Flood Control District and Department of Transportation also provide GIS datasets. Examples identified by the county include topographic contours, drainage infrastructure, street networks, and capital improvement project footprints.
Some products may be purchased directly, while certain products, including some topographic data, require additional information before fulfillment. For data picked up at the Flood Control District's Durango office, the county states that a Release of Public Information Form is completed at the front desk and that no advance action is required for that form. When an in-person visit is not possible, arrangements can be made to mail the data, although the Flood Control District does not cover shipping costs.
Historical Aerial Imagery
Maricopa County maintains a dedicated Historical Aerial Photography application for viewing imagery from different periods. The county's mapping directory states that historical aerial imagery dates back to 1930.
The application contains multiple imagery layers representing different acquisition periods. It also includes current parcel information, subdivisions, ZIP Codes, cities, township and range information, sections, streets, highways, mile posts, terrain information, contours, and spot elevations.
Historical imagery can be useful when the user's question concerns how a location appeared at an earlier time rather than what is shown in current imagery. Before searching, it helps to identify the approximate property or area and the year or period of interest. The application supports parcel-number searches and map-based selection, allowing a location to be identified before switching among available imagery layers.
The Historical Aerial Photography application also carries a county disclaimer stating that the Office of Enterprise Technology does not guarantee the accuracy or completeness of the information. Users remain responsible for verifying accuracy before accepting or relying on the displayed data.
Land Survey Point Mapping
Maricopa County's GIS applications also include a specialized Land Survey Points system maintained with Department of Transportation survey data. The map contains several categories of control and survey information, including MCDOT-approved control, primary and secondary control, National Geodetic Survey horizontal and vertical control, PLSS corners, corner records, section information, land subsidence layers, parcels, subdivisions, and other geographic reference information.
The system includes a selection tool that allows users to draw on the map and export selected survey data. Downloaded information is marked as an "Unofficial Document."
The Department of Transportation states that it has made reasonable efforts to maintain the survey data accurately but does not guarantee accuracy, completeness, timeliness, or correct sequencing. The department also prohibits downloads for commercial intent or resale except under an applicable sublicensing agreement. As with other county GIS products, the viewer or user is responsible for verifying information before acceptance.
Planning and Zoning Maps
Planning-related GIS information is provided through PlanNet. The application includes planning and zoning functions such as "What's My Zoning?" and a Community Residence Viewer.
PlanNet should be treated as a geographic visualization tool rather than an unconditional guarantee about a property's regulatory status. Its disclaimer states that Maricopa County has made reasonable efforts to maintain the data accurately but does not guarantee accuracy, completeness, timeliness, or correct sequencing. Use of the system constitutes acceptance of its stated terms and conditions.
When researching a property, users should avoid treating a parcel viewer and a zoning viewer as interchangeable. The parcel application focuses on Assessor-related property information, while PlanNet visualizes data used for planning and development. Selecting the system according to the question reduces the chance of relying on a layer that was created for a different county function.
Map Accuracy and Verification
Several Maricopa County GIS applications repeat a similar principle: mapped information should be verified before it is relied upon. This is especially relevant because county GIS systems combine information from different departments, update schedules, source records, and geographic layers.
A map can be useful for locating a parcel, identifying a geographic feature, comparing aerial imagery, or selecting data for further research, but the displayed geometry may not substitute for the underlying official record. The Assessor's Parcel Viewer specifically warns that its parcel boundaries are illustrative and are not equivalent to a real estate survey or title report.
Users should also pay attention to update timing. The Open Data Portal states that some datasets may be updated daily while others follow weekly or monthly schedules, and the Parcel Viewer expressly says that its information is not updated in real time. A current-looking map interface does not mean every layer was refreshed at the same moment.
Preparing for a GIS Search
The information to have ready depends on the GIS application being used. Preparing the most relevant identifiers before opening the map can reduce broad searches and help distinguish similarly located properties or features.
For parcel research, have the parcel number or APN when available.
For historical aerial research, identify the property or geographic area and the approximate imagery year needed.
For voting-location mapping, have the address used for the location search.
For survey data, identify the geographic area or control information relevant to the project.
For planning and zoning research, identify the specific parcel or location before reviewing planning layers.
For downloadable GIS data, determine the subject area and whether the needed information is available through Open Data or requires a departmental data request.
Users working across several systems should also keep identifiers consistent. An APN used in the Assessor's Parcel Viewer serves a different purpose from a map layer name, survey point, or planning classification. Keeping those identifiers separate helps prevent information from one system from being mistaken for the official record maintained by another department.
GIS Problems and System Status
When an application is not loading or appears unavailable, users can review the county's GIS system status page. The status service tracks GIS applications, GIS services, the GIS website, and related infrastructure. It identifies operational conditions as well as degraded performance, partial outages, major outages, and maintenance events.
Checking system status can help distinguish a county service interruption from a browser-specific problem. For Parcel Viewer search or parcel-detail problems, the application itself recommends clearing the browser cache. For the Historical Aerial Photography application, the county also advises users to clear the browser cache before first use.
Mapping Team Questions
Questions about a county GIS mapping application can be submitted through the official Contact Mapping Team form. The form requires a first name, last name, phone number, email address, the mapping application involved, and a message.
Identifying the specific application in the request is useful because Maricopa County operates multiple GIS systems. A question about Parcel Viewer behavior, historical aerial imagery, survey data, planning maps, or another mapping application can be routed more clearly when the application is identified rather than described only as "the GIS map."
When reporting a map problem, the message should describe what occurred and which application was being used. If the issue concerns a particular parcel or location, including the relevant parcel number or other search information in the message may help distinguish the geographic feature involved, provided that information is appropriate for the inquiry.
Common GIS Search Mistakes
Many problems with county GIS research come from using the wrong application or treating displayed information as more authoritative than the county describes it. Several mistakes are particularly easy to avoid.
Using One Map for Everything
Maricopa County GIS is a collection of specialized systems. Property assessment information, zoning, flood information, transportation data, historical imagery, election locations, environmental information, and survey points are maintained for different purposes. A parcel appearing in several maps does not mean those applications maintain the same underlying record.
Assuming Real-Time Updates
The presence of an interactive online map does not mean its data updates immediately. The Parcel Viewer states that its information is not updated in real time, while the Open Data Portal explains that dataset schedules vary from daily to weekly or monthly updates.
Treating Map Lines as Surveys
Parcel boundaries in the Assessor's Parcel Viewer are illustrative. The county warns that displayed adjacent parcel boundaries may not always match recorded documents and states that the information is not a substitute for a title report or real estate survey.
Ignoring Data Terms
Open Data and survey-data applications contain conditions concerning accuracy, redistribution, commercial use, and resale. Download access should not be interpreted as permission for every possible downstream use. Users intending to distribute or commercially reuse county GIS information should review the applicable conditions before doing so.
Confusing Open Data With Requests
Some county GIS information can be downloaded immediately through the Open Data Portal, while other products are handled by the Assessor's Office, Flood Control District, or Department of Transportation under separate procedures. Checking the Open Data Portal first can help determine whether a formal data request is necessary.
GIS Departments and Offices
Maricopa County Geographical Information System (GIS)
301 West Jefferson Street
Phoenix, AZ 85003
602-506-3011
Office of Enterprise Technology
301 S 4th Ave
Phoenix, AZ 85003
602-506-4357
GIS FAQs
Can the Parcel Viewer reopen the map where I left off?
Yes. The official Maricopa County Parcel Viewer includes an App State feature that can restore the map extent and layer visibility from a previous session. This can be helpful when you have already zoomed into a particular neighborhood and turned on the layers needed for your research. Keep in mind that restoring the map setup does not mean the underlying property information has been preserved as a permanent record. If you need documentation for later use, record the relevant parcel number and separately preserve any information you need to reference.
Can I limit a parcel search to the area currently on my screen?
Yes. When searching by parcel number, the Parcel Viewer provides an option to search only within the current map view. This is useful when you are working in a specific neighborhood or subdivision and want to keep the search geographically focused. The viewer also allows map-based selections and provides a search-tolerance option for point selections. These controls can make it easier to isolate nearby parcels when a broader search produces more features than you need.
How can I tell whether aerial photography exists for a certain year and location?
The county's Historical Aerial Photography map includes imagery layers from numerous acquisition periods, but coverage is not necessarily identical for every year. Many years have corresponding footprint layers showing the geographic extent of available photography, and the application also includes an "Aerial Photography Not Available" boundary layer. Checking these footprints can help determine whether a missing image is caused by unavailable coverage rather than a loading problem.
Is there a way to report usability problems with a county GIS application?
Maricopa County provides an official GIS Portal Website Survey where users can identify the application they were attempting to use and describe website problems or other feedback. The survey covers applications such as parcels, historical aerials, survey points, planning and zoning, flood-related maps, road closures, air quality, and mosquito management. Naming the specific application involved makes the feedback more useful than describing the issue only as a general GIS problem.