“If we had not approved gaming along these lines this year and put ourselves at the forefront, other states would have moved ahead of us and we would have been back in a year or two playing catch-up,” said Tom Cook, Delaware’s secretary of finance. He said that intense competition from Maryland and Pennsylvania was projected to drive down Delaware’s gambling revenues to $206.4 million in the year that began in July, from $248.8 million in the 2011 fiscal year.

The rapid expansion of gambling, as recession-racked states have searched for new sources of money, has transformed the industry. States that once enjoyed near-monopolies on gambling — including Delaware, which legalized slotlike machines at its racetracks in 1994, and New Jersey, which opened the nation’s first casinos outside of Nevada in 1978 — have been suffering the most in the new casino-dotted national landscape.

Atlantic City’s casino revenues have fallen by more than a third in recent years, according to an analysis by the Center for Gaming Research at the University of Nevada, Las Vegas. Pennsylvania, which opened its first casino in 2007, is overtaking New Jersey by some measures: over the past year Pennsylvania has taken in more slot machine revenue than New Jersey, according to Shawn K. McCloud, the vice president for analysis at Spectrum Gaming Group, a gambling research and professional services firm.

“The driving factor here is location,” said William R. Eadington, a professor of economics and director of the Institute for the Study of Gambling and Commercial Gaming at the University of Nevada, Reno. “Other things being equal, people will choose the most accessible or convenient casino outlets. People who used to travel some distance no longer do.”