http://tags.library.upenn.edu/project/40189 PennTags Feed for /project/40189 PennTags Feed http://tags.library.upenn.edu/makerecord/project/40189 http://tags.library.upenn.edu/makerecord/project/40189 Urban Studies Research Guides and Tools http://tags.library.upenn.edu/makerecord/url/40190 http://tags.library.upenn.edu/makerecord/url/40190 U.S. Census Research Guide http://tags.library.upenn.edu/makerecord/url/40192 http://tags.library.upenn.edu/makerecord/url/40192 Sanborn Maps Research Guide http://tags.library.upenn.edu/makerecord/url/40193 http://tags.library.upenn.edu/makerecord/url/40193 Key to Sanborn Maps, Philadelphia http://tags.library.upenn.edu/makerecord/url/40191 http://tags.library.upenn.edu/makerecord/url/40191 Architectural Research at the Philadelphia City Archives