Sanborn Fire Insurance Maps of Salisbury, Hebron, and Mardela Springs, Maryland, as well as Ocean City, Maryland. These maps document the roads, facilities, and physical structures of the region in detail. Includes a reproduction of the 1888 map and original copies of maps from 1931; physical additions to the 1931 map were made in 1942, 1946, and 1951. The Ocean City map originally dates to 1936 and additions were made in 1941.

The Sanborn maps themselves are large-scale lithographed street plans at a scale of 50 feet to one inch (1:600) on 21 by 25 inches (53 by 64 cm) sheets of paper. The maps were published in volumes, bound and then updated until the subsequent volume was produced. Larger cities would have multiple volumes. In between published volumes, updates (new drawings of new or altered buildings or lots) were created and sent out to be pasted on top of the old maps (referred to as ‘slips’) to reduce expense and still preserve accuracy.

The map volumes contain an enormous amount of information. They are organized as follows: a decorative title page; an index of streets and addresses; a ‘specials’ index with the names of churches, schools, businesses etc.; and a master index indicating the entirety of the mapped area and the sheet numbers for each large-scale map (usually depicting four to six blocks); and general information such as population, economy and prevailing wind direction. The maps include outlines of each building and outbuilding; the location of windows and doors; street names; street and sidewalk widths; property boundaries; fire walls; natural features (rivers, canals, etc.); railroad corridors; building use (sometimes even particular room uses); house and block number; as well as the composition of building materials including the framing, flooring, and roofing materials; the strength of the local fire department; indications of sprinkler systems; locations of fire hydrants; location of water and gas mains; and even the names of most public buildings, churches and businesses.

Sanborn Maps is an American publisher of historical and current maps of US cities and towns. The maps were initially created to estimate fire insurance risks. The company's maps are frequently used for historical research, and for preservation and restoration efforts.