By reference to the key map (fig. 1) it will be seen that the Johnstown quadrangle is in southwest-central Pennsylvania. It lies mostly in Cambria County but covers also small parts of Somerset, Westrmoreland, and Indiana counties. Most of it is included in the valley of Conemaugh River and its tributaries Little Conemaugh River and Stony Creek, at the confluence of which is Johnstown and its suburbs. The northern part of the area is in the valleys of Blacklick Creek and it South Branch, along which are the small but prosperous coal-mining town Nanty Glo, Twin
Rocks, Weber, Vintondale, and Wehrum.