The Grays began playing in the forerunner of the Eastern League, the old New York–Pennsylvania League in 1923. The Class B league was made entirely of teams from New York and Pennsylvania. It kept this name until 1938 when the Scranton Miners move to Hartford, Connecticut. Williamsport was a member of the league for 46 years between 1923 and 1991. The teams were known as the Grays, Tigers, A's, Mets, Tomahawks and Bills. Williamsport had affiliations with the Philadelphia A's for three periods, Pittsburgh Pirates, Detroit Tigers, Washington Senators, Philadelphia Phillies, New York Mets, Cleveland Indians for two separate periods, and Seattle Mariners.