Scott Detrow and I mapped drilling for NPR’s StateImpactPA site:

First, while 32 counties host gas wells, the bulk of activity is still taking place in a handful of drilling-heavy counties. More than 60 percent of the 739 wells drilled between January and June were located in the five busiest counties — Bradford, Tioga, Washington, Susquehanna, and Greene. Bradford and Tioga Counties alone are responsible for nearly 40 percent of 2011 drilling activity. Here’s a proportional symbols map of wells drilled: