SF State students might be surprised to learn that the city had a winning minor league baseball team in the Mission District long before the major league Giants arrived.

"The caliber of baseball played was equal to the big leagues," said 73-year-old Bill Soto-Castellanos, who started his San Francisco Seals career as a bat boy in 1951 and ended it as the visiting team's clubhouse man in 1957. "And the Seals Stadium was like a major league ballpark."

The Seals had a reputation for innovation, cultivation of local talent, record game attendance and tireless promotion of America's pastime in San Francisco.

Founded in 1903, the Seals were part of an eight-team, west coast minor league division called the Pacific Coast League, Soto-Castellanos said.

The team won 10 PCL pennants between 1903 and 1957, according to the book "The San Francisco Seals, 1946-1957" by Brent Kelley.

San Francisco gained a sporting edifice it could boast about when Seals Stadium opened in 1931. The complex occupied a large plot bounded by Alameda Street, Potrero Avenue, 16th Street and Bryant Street. Over the years it has featured - among other things - outdoor lighting, indoor concessions, female usherettes, barber shop, and a live seal in a tank, according to Sato-Castellanos. It also hosted another San Francisco-based PCL team during 1931-1937: the Mission Reds.

Popular San Francisco native, one-time Seal and former major league player Francis "Lefty" O'Doul became Seals manager in 1935 and stayed until 1951, according to Kelley's book. It was during O'Doul's tenure that notoriety for the three DiMaggio brothers from North Beach soared. "Joltin'" Joe DiMaggio went on to become a New York Yankees legend and a member of the Baseball Hall of Fame.

"As manager of the San Francisco Seals, O'Doul was recognized as one of the finer strategists and talent developers, sending players such as Joe and Dominic DiMaggio to the majors," said Kathy Killmeyer Temby, manager of the Bay Area Sports Hall of Fame.

At the request of U.S. General Douglas MacArthur in 1949, O'Doul took the Seals to Japan as part of a post-World War II goodwill mission, according to Soto-Castellanos. Credited with bolstering interest for the sport there, he would gain title "Japan's Father of Baseball."

The growing popularity of television and baseball broadcasting in the 1950s eroded game attendance. And team owner Paul Fagan - who had once morphed Seals Stadium into a top-notch venue the equal of major league parks - gave up on his aspirations of transforming the Pacific Coast League into the third major league, according to Soto-Castellanos.

The Seals ended their 1957 season with a bang by securing the pennant, but it wouldn't be enough to stave off the inevitable: Minor league baseball was finished in San Francisco.

With the Seals gone, the stadium was granted a two-year reprieve as a temporary home to the major league Giants relocating to San Francisco from New York. But when the Giants shifted to the newly constructed Candlestick Park, Seals Stadium became surplus and succumbed to the wrecking ball during the final weeks of 1959, according to Soto-Castellanos.

Today, the site is occupied by the Potrero Center shopping complex.

But more than a half century after the Seals left San Francisco, many still remember and recognize the team's importance.

"The interest level is so high, it's astounding," said Soto-Castellanos, who later wrote a book about his experience with the team entitled "My Life and Education with the San Francisco Seals."

Shana Daum, director of public affairs for the Giants, said of Seals Plaza at AT&T Park, "There is a statue of a seal out there and a commemorative plaque that recognizes the San Francisco Seals as the predecessors that laid the foundation for bringing major league baseball to the West Coast and to San Francisco." The Giants' mascot is also a seal by the name of Lou Seal.

Opposite the Seals Stadium site, the aptly named Double Play Bar and Grill celebrated its centennial recently and is a trove of Seals lore.

"We have lots of pictures of Seals players and memorabilia here," said Martin Coyne, owner of the Double Play. "We still have older guys come in that went to ballgames there [Seals Stadium]."