They played as far north as Canada's Cape Breton League, and games against mill or industrial teams in Maine, Vermont and New Hampshire.
Black sports teams often named themselves after cities that would immediately identify them as African American to white fans and media (such as the Harlem Globetrotters, who were founded in Chicago).
Negro league superstar Bill Yancey, later a New York Yankees scout, said Jackman was the greatest all-around ballplayer he ever saw.
According to James A. Riley's "Biographical Encyclopedia of the Negro Leagues," Jackman was "52-2 one season with the Giants and bested Satchel Paige twice in two outings."
Longtime Negro league pitcher Pud Flournoy pitched for the team when he was past his prime, and centerfielder Gene Benson told a Black baseball author the Royal Giants left him stranded in Michigan during a road trip.