Contrary to popular belief, Baseball was not invented by a single individual, but evolved from various European “bat and ball” games. In New York City, in 1845, Alexander Joy Cartwright, Doc Adams and others were early members of a group of young professionals who made up the Knickerbocker Base Ball Club.
The Knickerbockers began the process of formalizing the rules (e.g. bases set at 30 paces or 90 feet apart, establishing foul territory, etc.) in the late 1840s and early 1850s. Establishing clear foul territory was a major improvement as it allowed spectators to get up close enough to the action to become more interested in the game.
Base ball was played during the Civil War. Interest in the game grew immensely in the post-war years. As the popularity (and prospects for getting paying spectators) grew, still more professionalism crept into the game. Eventually, Harry Wright’s Cincinnati Red Stockings fielded the first, openly all-professional team in 1869. In 1876, the National League was established, and the rest is history as base ball evolved into America’s National Pastime.