As with a lot of history, the origin of baseball cannot be narrowed down to one single date. From the best estimations we know that the game originated from the British sports of cricket and rounders, somewhere in the mid-1700s to early-1800s. The early 1800s saw the game come to the United States, where it has since flourished.

The popularity of the game spread across the northeast US in the following years. Both the New York and Massachusetts games had staunch adherents at first, but the New York game became more popular after the formation of the National Association in 1857. A rival organization for the Massachusetts game appeared also, but its popularity faded and the New York game survived to evolve into the game we know today.

During the American Civil War the game played in the camps of both armies. By 1865 91 clubs were represented in the National Association of BaseBall Players, from as far west as Kansas. All the clubs were amateur, but in 1869 the Cincinnati Red Stockings declared that they would henceforth be a professional side, and within 10 years professionalism was thoroughly established.

In 1870, a schism formed between professional and amateur ballplayers. The National Association split into two groups. The National Association of Professional Base Ball Players operated from 1871 through 1875, and is considered by some to have been the first major league. (Other researchers dispute this.) Its amateur counterpart disappeared after only a few years.