Fire insurance maps are a core resource for documenting the development of neighborhoods over time. Founded in 1867, the Sanborn Map Company was the primary American publisher of fire insurance maps for nearly 100 years. They show lot numbers, square footage of lots, street addresses, which lots have buildings and their shape and materials. They indicate the type of construction, property lines, and the number of stories. They can narrow the date when a building was constructed. They can be used to track demolition, recent construction and alterations. They identify plot numbers necessary to access deed and other civil records.
If, for example, you're most interested in area around Brookes Avenue in the Capitol Heights neighborhood just south east of Washington, D.C. use the following steps to get a closer look of the specific neighborhood or street.
To find the appropriate map sheet, click on the index map (sheet 0a). It will open in a new window. Because Washington, D.C. is a larger city, there are several volumes of this map; however, only the second volume from 1939 is available to us. Select the index key in volume two.
To enlarge the display window, select a larger blue box from the "select window size" option. This will make the display area larger, but you may have to increase your browser window accordingly. You can also zoom in on the image using the "Zoom" drop-down menu or click on the map to zoom in.
There are two ways to navigate around the display window: by clicking on the arrows on the four sides of the box, or by clicking on the re-center button at the top of the box. When re-center is selected, clicking on a point in the window will redraw the image with the selected point at the center.
Use all of the previously mentioned tools to get a closer look at the area around Brookes Avenue in Capitol Heights. The large numbers on the map tell you on which sheet you can find a more detailed, close-up map of this area.
Select a map using the thumbnail or scrolling menu. For our purposes, use sheet 450 to get a closer look at Brookes Avenue in Capitol Heights. Minimize the index map and take a look at the thumbnail page. If sheet 450 is not displayed, select it by clicking on it in the drop-down menu at the bottom of the thumbnail page. A new viewing window will open with just sheet 450 in it. The window with sheet 0a in it, the index map, will not close or be reloaded, allowing us to look at several sheets at once. With sheet 450, you can now find more detailed information about the neighborhood around Brookes Avenue, as well as the specific building numbers.
Displaying and Working with the Maps - Visual Steps
Start with Washington DC, 1939, Index (Sheet 0a):
To zoom, use any of the options at the top of the window:
Once you have zoomed in, you can see that you need sheet 450:
To get to sheet 450, click back to the page showing the thumbnails of all the sheets. At the bottom of the page use the "Jump to sheet" dropdown menu:
Sheet 450 from the 1939 Washington DC Sanborn Map:
Once you are zoomed in, you can navigate using the blue arrows: