Pennsylvania is the 19th U.S. state to have marriage equality.
A 1996 state law defined marriage as only acceptable if a man and a woman did it. In the case just decided today the state's attorney general (Kathleen Kane - D) did not act as the defense, but the governor (Tom Corbett -R) did.
Apparently the courts did not think that Pennsylvania has the right to discriminate against people.
...31 left to go.
Edited to add: here's the decision in case you like reading judicial decisions. Here's part of the conclusion:
In the sixty years since Brown was decided, "separate" has thankfully faded into history, and only "equal" remains. Similarly, in future generations the label same-sex marriage will be abandoned, to be replaced simply by marriage. We are a better people than what these laws represent, and it is time to discard them into the ash heap of history.