"Most people don't know the history of their street, neighborhood, or even city. The Pittsburgh Mapping and Historical Site Viewer
provides a window into the past, allowing anyone to see how the city took shape over time. It shows how the city of 22,433 people in 1835 changes over time: how neighborhoods grow and expand, while others were planned but never built. Street names change over time, empty lots become buildings, and schools and churches open and close...The maps were made by cutting and georeferencing hand-drawn paper maps made over 100 years ago [the G.M. Hopkins maps online in Historic Pittsburgh
]. Using historic maps, some more than 175 years old, this interactive map highlights sites in the National Registry of Historic Places among others."