Mariner Square Athletic Club was built in 1978 and went by the name of Supreme Courts. During those early years it was a racquetball club which housed Nautilus of Alameda. In 1981 Kathy Wagner became the owner of the facility, complete with 16 racquetball courts, a snack bar and eight employees. Since that time Kathy Wagner has kept up with the ever-changing fitness industry. During the mid-1980’s an indoor swimming pool was built, courts were converted into fitness centers and the snack bar was remodeled into a full functioning cafe. Over the years various other renovations have helped to keep MSAC a leader as one of the East Bay’s largest full-service health clubs.