New Delhi, June 26 -- BATON ROUGE - When Bally's Baton Rouge opened its permanent land casino in December after years squeezed into a temporary riverboat facility, Louisiana's gaming regulators expected improvement. The May numbers from the Louisiana Gaming Control Board suggest they may have underestimated how much.

Statewide casino revenue reached $246.2 million in May, up 8 percent from the same month a year earlier, according to the board's report released Thursday. Strip out Bally's Baton Rouge and the increase narrows to 5.7 percent. The difference between those two figures is the story of one building's transformation, and what it does to a state's monthly totals.

The broader Louisiana gaming industry is in an expansion phase. Al...