(FORTUNE Magazine) – If you're going to dislocate your shoulder, there's no better place to do it than Schmitt Field in Rochester, Minn. It's a stone's throw from the Mayo Clinic, which is where Brent "Skinny" Peterson--captain of the St. Croix Base Ball Club of Washington County--was taken, via ambulance, during the championship match against the Rochester Roosters, with state bragging rights and the Silver Ball riding on the outcome.

The ambulance was one of the few 21st-century intrusions on the pristine July day. The rest of the afternoon onlookers watched base ball as it was played (and spelled) in 1860. It's like a Civil War reenactment--with bats instead of guns.

On any summer weekend upwards of 130 teams are doing the same, from the Glen Head Zig Zags of Long Island, N.Y., to the Wahoo Plowboys of Nebraska. (Most names come from actual 19th-century clubs.) And the sport's on the rise. John "Stinky" Freyer, a member of the Deep River Grinders of Hobart, Ind., and the communications director for the Vintage Base Ball Association (VBBA), says that 50 teams have formed in the past three years, and he's fielded inquiries from Atlanta to Washington State.

Ranging in age from 15 to 70, the vintage "ballists"--some sporting muttonchops not seen since Shiloh--play on fields that would make Derek Jeter blanch (trees straddling third base, a mobile home in right); wear uniforms stitched by their wives; and use authentic balls made of India rubber, yarn, and one piece of leather, and bats that are longer and heavier than today's. The bases at Schmitt Field are canvas bags of sand. And they use words like "behind" for the catcher and "three hands down" for the end of the inning. A ball caught on a bounce (fair or foul) is an out.

Vintage base ball players tend to agree on little, but there's a consensus that the first game was played in 1980 at Old Bethpage Village on Long Island. The following year Amos Loveday at the Ohio Historical Society in Columbus founded the Ohio Village Muffins. With no teams to play, the early clubs rustled up games against any opponents they could find. As time went on, they hit the road and inspired other teams to form, which is why Ohio and New York are the sport's two strongholds, each with more than a dozen clubs. Then more sprang up in New England, the Midwest, and beyond.

Vintage base ball is part sport, part history lesson, and part entertainment, and different teams emphasize different aspects. On one side you have the Ohio teams, who exaggerate the shtick for the benefit of spectators (called "cranks"). "It's like bad vaudeville," says Doug Smith of the Muffins, who play about 50 games a year and even have an all-women sister club, the Lady Diamonds. The Muffins' umpire (most teams have their own) puts on a good show. If a fan is clad in shorts, he'll exclaim in mock horror, "How dare you bare your knees with ladies present!"

On the more competitive side are the nine Bethpage teams. "At first we had historians playing baseball," says Ken Balcom of Old Bethpage, "but I got baseball players to be historians." They're divided into two leagues, one following 1860s rules, the other following rules from 1887. Rules changed often in the early years; one major difference was that pitchers threw underhand from 45 feet away in 1860 and overhand from 55 1/2 feet by 1887. (New teams often adopt whatever rules were in place when their namesakes began playing.) And not all rules are clearly defined--for example, the 1860 rules make no mention of stealing or sliding, which is practiced by some clubs but eschewed by others.

One would think that the east-west debate would be best settled on the field, but since most teams have limited funds, it's rare to see a New York team show up in Ohio or vice versa. Joining a team can tax a player's wallet (up to $500 a year) and loved ones. "It puts stress on a lot of relationships," says VBBA president Mark Heppner.

Speaking of stress, what of Skinny's shoulder and the St. Croix nine? They held on to beat the Roosters 3-1, capturing the Silver Ball. Says pitcher Don "Pieso" Hammer: "It was one of the best games we've played."

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