In the date list you will sometimes see a range of dates, such as 1894-1895. This range indicates the date the mapmakers began work on the map and the date of completion. In later years the Sanborn Company issued revisions that were intended to be literally pasted over the original map sheet. In these cases, the last date refers to the date of the most recent pasted correction. Digital Sanborn Maps, 1867-1970 includes versions of maps with and without these pasted corrections. Our collection, originally microfilmed from the Library of Congress' collection, includes all maps submitted to the Library through copyright deposit in their original form and a set of maps including pasted corrections that was transferred to the Library from the Bureau of the Census.
In some cases, you may notice the same date listed twice for a city or listed once as a single year and a second time as the first date in a range. These two dates correspond to the two versions: one deposited to the Library by the Sanborn Company and one transferred from the Bureau of the Census, which may contain pasted corrections not on the other version. If a map is from the Bureau of the Census, an asterisk (*) will follow the date in the date drop-down menu.
The drop-down menu may also contain an entry for "new and additional sheets." These are updated sheets created by the Sanborn Map company intended to replace sheets of previous maps. The image of the sheet will refer to what sheet it replaces.
Bound volumes, each containing approximately 100 sheets, were created for large cities. In Digital Sanborn Maps, 1867-1970 if you select a map that is divided into volumes, you are automatically taken to the first volume in the set. The best way to navigate a volume is to find the key sheet which provides a birds-eye view of the city indicating which areas of the city are in which volumes. Volumes are specific to the date or date range you select in the date drop-down menu. Dates or date ranges listed next to the volume number indicate how current the sheets are in that volume by letting you know the time period when that volume was created. For example, it may have taken less time to create a single volume (volume date range) that it took to create the entire city (date you selected in the drop-down menu).
Each Sanborn Map is divided into numbered sheets, each approximately 65x55 cm. If you arranged all the sheets together on the floor, you would have a complete, but very large map! Because streets and buildings are located on various sheets, you need to use the key and index sheets to navigate.
Maps with several sheets also include a key sheet and/or an index sheet. A key sheet provides a birds-eye view of the city. You will be able to see sheet numbers (or volume numbers) over different areas of the town. You can then browse the sheet thumbnails to pull up the sheet you are looking for. An index sheet provides an alphabetical list of streets (usually including block numbers) and prominent buildings, labeled "specials." The index refers you to the sheet number for that address or building.