Bisbee Copper Kings co-owner Tom Mosier said his team's home field, Warren Ballpark in Brisbee, was established in 1909, one year before Rickwood Field in Birmingham, Ala., The Arizona Republic in Phoenix reported Tuesday.
Mosier and others said they take issue with Rickwood Field officials claiming to have the oldest ballpark in the United States.
"They need to be able to subtract 1909 from 1910," Mosier said.
Tim Wiles, Baseball Hall of Fame research director, said both cities have a "legitimate claim to call it the oldest ballpark or field, if you qualify it in some way."
He said different possibilities include being the oldest continuously used ballpark or the oldest professional ballpark.
"It would take a Philadelphia lawyer to figure out why each one of these makes an essentially legitimate claim to be the oldest ballpark," Wiles said. "I'd hate to take it away from any of these places."