Most of the professional baseball teams in Baltimore have been called the Orioles, in reference to the bird. There was already a minor league Baltimore Orioles, and the new Federal League club built their ballpark directly across the street from the Orioles park. The new club chose to call itself the Baltimore Terrapins, after the diamondback terrapin, the state reptile of Maryland.

After the war ended in 1945, Eddie Harris and David P. Portlock began the process of organizing a Negro league in the area using the current minor league Pacific Coast League stadiums while those teams were on the road. They reached out to Abe Saperstein to assist. Saperstein already owned a barnstorming team called the Cincinnati Crescents, which he moved to Seattle and renamed them the Seattle Steelheads. He knew Jesse Owens, the track and field athlete and four-time gold medalist, and asked him to join. Owens formed the Portland Rosebuds in Oregon. Saperstein was elected league president, Owens vice-president and Portlock secretary. A 110-game season was planned. However, the league survived for only about three months. Most teams played under 30 games and the league folded due to poor attendance, a lack of financing, and difficulty in accessing ballparks. Seattle, Los Angeles and Oakland continued the season playing local teams across the midwest.