The results represent a nearly 22 percent increase from 2010, the Pennsylvania Gaming Control Board said.

Gross revenue is the amount left over after payouts, or the amount that gamblers lost.  Slot-machine revenue rose almost 6 percent to $2.4 billion, while table games revenue almost doubled to $619 million. Table games were legalized in early 2010 and the casinos didn't install the games until at least midway through that year.

Pennsylvania's first casinos opened in 2006, and are already threatening to surpass Atlantic City, N.J., as the nation's second-largest gambling market. In 2011, Atlantic City's casinos won $3.3 billion, down nearly 7 percent from 2010. Atlantic City has 11 casinos, and another that is expected to open soon.

Atlantic City has been hurt by the recession, racetrack casinos in New York and Delaware and Pennsylvania casinos that are giving gamblers who had long been a key part of Atlantic City's customer base a much closer-to-home option.

Instead of a three-hour round trip to Atlantic City, more than two-thirds of Pennsylvanians are now within an hour's drive of a casino in their own state. Atlantic City has been struggling, without much success, to try to replace that revenue.

The city's troubles could deepen with the introduction of big-time gambling in New York and

Massachusetts, while Ohio is poised to see its first commercial casinos open this year and Maryland's first casino opened last year, with more on the way.

Read More|Comment