From a recent EIA report on domestic oil and natural gas reserves: "Proved wet natural gas reserves decreased in four of the top five U.S. gas reserve states (Texas, Wyoming, Louisiana, and Oklahoma) in 2012 ***. Pennsylvania was the only state in the top five to report an increase (9.8 Tcf) in natural gas proved reserves in 2012, as a result of development of the Marcellus Shale play. In 2012, Pennsylvania went from fifth to the second largest gas reserve state."
Graphically: