Historical Map – Philadelphia Rapid Transit Co. Trackage Map, 1910
What appears at first glance to be a street map of Philadelphia in the early 20th century is actually not what it seems. All this map depicts is streetcar track and mainline railroads (in traditional ticked lines), showing how incredibly dense the streetcar network was at the time, especially downtown. Interestingly, a lot of the system appears to be single-track only.
Nowadays, only a few vestigial trolley lines recall the days when streetcars reigned supreme in Philly.
Source: Wikimedia Commons