This detail from an 1860 map shows the buildings, yards and alleyways that existed on a portion of the southern most block of Independence Mall. These kinds of Sanborn maps help archeologists plan their digs.
(Map: Free Library of Philadelphia).
Before the Digging Begins
Long before the first shovel full of dirt is turned, a detailed background study is prepared for the areas where construction will take place. Documentary records in libraries and archives are searched for information on the history of the sites. Using maps, tax records, deeds, and other official records, along with diaries, letters and other historical sources, archeologists gather a detailed picture of the history of the project area. Records reveal who lived and worked on the blocks, how the residential and commercial character of the area changed over time, and what portion of the former landscape might have escaped destruction during hundreds of years of development and change.