Researching property history in Arizona, Part 4: Plat Maps

(This is Part 4 of a series written by Research Library team member Chris Seggerman. Read Part 1. Read Part 2. Read Part 3.)

What does a neighborhood look like before it exists? How do blank square-mile sections fill with ordered rows of streets and houses? How does a developer sell that plan to investors or request development rights from the city and county for that neighborhood? Before the first shovel broke ground to build your neighborhood, those who planned it used a plat map.

Plat maps are filed by book and page number at the Maricopa County Recorder’s Office. The originals eventually pass to the State Archives. You can view unofficial copies of the maps here*.

This website wants you to enter the book and page number. That information can be found on a deed. The Maricopa County Assessor’s office also has links to this information on their parcel viewer.

Plat map example
(Image credit: C. Seggerman photograph of the original map located at the Arizona State Archives)

Historic plat maps are also interesting from aesthetic perspective. They predate computer-aided drafting, and some are practically works of art. They provide direct clues how a neighborhood used to look. The plat map for the Capitol Addition—Book 1, page 62– shows Tract A set aside for the site of the State Capitol, and other details. It shows the Valley Street Railway Company’s route down Washington Street. It also shows that several streets have changed name: Bingham became Monroe, Franklin became Adams, and Johnstone became Jefferson. It also shows that lots surrounding the capitol are small and narrow—a detail visible in slightly later aerial photos of the area.

Plat map example
(Image credit: C. Seggerman photograph of the original map located at the Arizona State Archives)

Some neighborhoods are platted by corporations. Other early plats show groups or individuals who gave neighborhoods now forgotten names. Simm’s Addition, registered with the County Recorder by James T. Simms in 1893, sits between Central and Third Avenue, just south of Interstate 10. Two of its streets, Westmoreland and Portland have parks in the middle of their streets, but only Portland remains. Westmoreland is now occupied by the Japanese Friendship Garden and the Irish Cultural Center, near the park. Interested researchers could construct the layout of the many neighborhoods sacrificed to Interstate 10 using plat maps alone.

You can also find development details you might not have thought about. For example, the area around Scatter Wash, where I walked home from high school, is a drainage easement. I grew up in terror that Scatter Wash might eventually be developed instead of remaining full of trees, bike ramps, and winding footpaths. The plat map explains “…no structure of any kind be constructed or any vegetation be planted nor allowed to grow within the drainage easements which would impede the flow of water over, under, or through the easements. The City of Phoenix may, if it so desires, construct and/or maintain drainage facilities on or under the land in the easements.”

That did not stop the City of Phoenix from clearing some vegetation and slightly reshaping the wash in the late 1990s, but the plat map explains that area will probably always remain undeveloped.

*If the electronic copy of the plat map at the County Recorder’s website is difficult to read, you can see the early originals at the State Archives or at the Recorder’s office.


Arizona Territorial Census Records Now Available Online!

A significant group of valuable Arizona historical record collections, provided through a partnership with the Arizona State Archives and, are now available on-line and free to residents of the State of Arizona through  This includes the Arizona territorial census records covering the years from 1864 through 1882.

All Arizona records are available at and can be found on the Doing Research at the Archives page or directly at

This access requires a free Arizona account. To set up your account you simply go to the web page and enter your five digit Arizona zip code in the space at the bottom of the page.  Once your account is established researchers gain unlimited access to Arizona records that are a part of the State Archives of Arizona’s extensive holdings.

Congratulations Chris!


Chris Seggerman, Genealogy Researcher was recognized at today’s meeting of the Arizona State Library, Archives, and Public Records Advisory Board meeting for rising to the occasion and ensuring a smooth transition of the genealogy collection to the Polly Rosenbaum History and Archives Building. Pictured left to right: Secretary of State Michele Reagan, Chris Seggerman, Library Advisory Board Chairman Brenda Brown.

To learn about the genealogy resources at the Polly Rosenbaum History and Archives: (this link no longer works as we no longer have a separate genealogy collection. However, you can click HERE to see what genealogy material we still have in our catalog.)

To learn more about the advisory board:  (link still works, however the Advisory Board Of The Arizona State Library, Archives And Public Records was repealed effective August 9, 2017).

Have old family photographs?


Have an old letter or other paper-based object you’d like to preserve? Appointments are available for one-day only on 10/14 with Arizona State Conservator Siegfried Rempel of the Arizona State Archives. Call 602-926-3720 and schedule your appointment today! The appointments will be in the Polly Rosenbaum Archives and History Building located near the state capitol mall at 19th avenue, just south of Jefferson street in Phoenix.