The Library of Congress has been digitizing its collection of Sanborn Fire Insurance Maps for a few years, and recently the institution added a number of Delaware products to its website. To produce the atlases, the Sanborn Fire Insurance Maps surveyors visited towns all across the nation to frequently update drawings and produce sketches at a detailed scale of one-inch to fifty-feet. With these sources a researcher is able to observe the changes that took place with structures and communities over generations. The Company was particularly active from the 1880s until the decades after World War II.
The online, digitized collection, which is accessible for free presently includes:
Camden – 1897
Clayton – 1897
Delaware City – 1885; 1891
Dover – 1885; 1891; 1897
Frederica – 1885; 1891;
Georgetown – 1885; 1891; 1907;
Harrington – 1885; 1891; 1897
Laurel: 1885; 1891; 18976
Lewes – 1891; 1897
Middletown – 1885; 1891
Milford – 1885; 1891; 1897
New Castle – 1885; 1891
Newark – 1891
Seaford – 1885; 1891; 1897
Smyrna – 1885; 1891
Wilmington — 1885
These maps are highly detailed and a lot of symbols and colors are used to catalog the data fire insurance underwriters needed. Here is a link that provides information on how to interpret the map symbols
In addition, there is a collection of Maryland Maps available online.
This link will take you to the Maryland collection
