On January 22, 1857, the National Association of Base Ball Players was founded in New York. The first organization governing American baseball, it terminated the Knickerbocker era when that club privately deliberated on the rules of the game.

Prior to the American Civil War (1861–1865), the beginnings of baseball competed for public interest with cricket and regional variants of baseball, notably town ball played in Philadelphia and the Massachusetts Game played in New England. In the 1860s, aided by the War, "New York" style baseball (as often played by Union Army troops passing the uneventful days of camp life between occasional skirmishes and battles) expanded through various corps, regiments, brigades, and other units into a national game.

In addition, the parallel civilian NABBP, as its governing body, expanded into a true national organization, although most of the strongest clubs remained those based in New York City, Brooklyn and Philadelphia.

By the end of 1865, almost 100 clubs were members of the "National Association" organization. By 1867, it had over 400 members, including some clubs from as far away as the Pacific Ocean west coast in San Francisco and south to the Gulf of Mexico coast in Louisiana.

According to Wikipedia