The Milwaukee Brewers spent their first season, 1969, as the Seattle Pilots in Seattle. Seattle was the third largest urban area on the West Coast and it was a realistic location for a Baseball team. The Cleveland Indians considered a move to Seattle in 1964 and 1967 the Kansas City Athletics considered a moved but ended up going to Oakland.
Seattle had to wait until 1977 till Major League Baseball returned in the form of the Mariners