One of the best known black baseball teams, the Homestead Grays' ballclub was organized in 1910, and Cum Posey, who would become the owner of the team, joined it as a player in 1912. Homestead was a steel mill town, and the workers at the U.S. Steel mill formed a baseball team for weekend recreation. Posey, a former football player and basketball star at Penn State University, was a railway mail worker and joined the steelworkers to play for the team. Playing on West Field in Homestead. the team began also playing twilight games during the week in addition to weekends. New players kept joining the team, and their reputation increased to the point of their becoming the leading attraction in the tri-state area. At first they added a little comedy to the game to enhance their appeal as a good gate attraction.

Soon after Posey started handling the team, it became a full-time job. He booked all the leading teams around the Pittsburgh area and, with the Grays playing as an independent team, made a good profit every year from 1912 to 1929. They joined the American Negro League in 1929, but the league lasted only one year. The next two seasons the Grays fielded its strongest teams since the franchise's inception, winning eastern championships both seasons. The 1931 club is called by many the greatest black team of all time.

But when the Depression hit in the thirties, there were some lean years for the Grays, and Gus Greenlee took advantage of Posey's economic situation to lure some of his best players to the Pittsburgh Crawfords. With no league in the East and the collapse of the Negro National League in the West, in 1932 Cum Posey organized the East-West League, but it didn't even last the year and folded in June.

In 1933 the Negro National league reorganized, and a year later, with Posey forming a partnership with Rufus "Sonnyman" Jackson to bring some money back to the organization, the Grays entered the Negro National League as associate members and became full members the following year, fielding a team each year until the league folded after the 1948 season.

During this time the Grays dominated the league, building a dynasty around the power tandem of Josh Gibson and Buck Leonard, dubbed the "thunder twins" and also called the black Babe Ruth and Lou Gehrig by the media. The Grays won nine consecutive Negro National League pennants, 1939-1945, and also annexed the last flag in 1948. During this time they also played in five of the seven World Series played between the Negro National League and the Negro American League, including the first and the last of these Series. They lost the first Series to the Kansas City Monarchs in 1942 and lost to the Cleveland Buckeyes in 1945, but defeated the Birmingham Black Barons in each of the other three Series, in 1943-1944 and 1948. After the league broke up the Grays continued to play for two more years as an independent team, playing against lesser opposition, but disbanded after the 1950 season.