Includes more than 660,000 Sanborn maps charting the growth and development of more than 12,000 American towns and cities. The digital collection was created from ProQuest Information and Learning's microfilm collection filmed from the Library of Congress' collection. The Library's Sanborn collection includes all maps submitted to the Library through copyright deposit and a set of maps transferred to the Library from the Bureau of the Census. Maps from the Bureau of the Census include corrections issued by the Sanborn Company that were pasted over the original map sheet. Maps acquired through copyright deposit remain in their original form.