I’m gonna have to score this one an error.. first of all, base ball really became the national game during the Civil War, and the soldiers brought it back to their local communities. The National Association would be playing league games in 1871, and that lead to the National League in 1876. The team known today as the Chicago Cubs played their first game about two months before Little Big Horn.
Also, the fable of Abner Doubleday was more or less invented by team owners/businessmen in the early 1900s, they wanted to quash talk that baseball had evolved from the British game of “Rounders”. Actual baseball historians give Alexander Cartwright much more credit for inventing the American game, but even there Cartwright is thought to be among a group of early (circa 1837-46) New York area players who developed rules for different ball clubs to meet in competition.