During the mid 19^th century, as American cities grew, many fire insurance  companies replaced on-site inspection of residential, industrial and commercial buildings with detailed maps showing the location,
construction, and function of all buildings in a community.  The Sanborn Map and Publishing Company of New York became the leader in this business.   Sanborn maps generally documented each city block, and every few years, as the city grew, a new set of maps was drawn to depict various changes. Sanborn maps thus provide an
invaluable research tool for historians
interested in studying the dynamics and
development of American cities and towns.

An examination of insurance maps can make an excellent introduction to a unit on community history.  Have students examine a series of Sanborn maps covering 20, 30, or more years in your community's history. 
Document land-use patterns, chart economic growth or decline, discuss diversity in business, and follow the town's expansion and development.

Choose one or two buildings that appear on Sanborn maps over several years.  Do the buildings change in any way from year to year?  When were additions made?  When was plumbing installed?  Electricity?  What materials were used in the construction of the building?


Have students compare and contrast a collection of Sanborn maps with
aerial photographs of your community from the same time period.  What information does each source provide and how do these two sources
complement each other?