Baseball's Beginnings
The history of baseball in the United States can be traced to the 18th century, when amateurs played a baseball-like game by their own informal rules using improvised equipment. The popularity of the sport inspired the semipro national baseball clubs in the 1860s. During the Civil War a rumor began that Abner Doubleday started baseball, but in reality baseball as we know it probably was first documented by Alexander Cartwright. The answer to the question of who started baseball is still unanswered and will likely remain that way.
The First Professional Baseball Team
The Cincinnati Red Stockings of 1869 were baseball's first openly all-professional team, with ten salaried players.The Cincinnati Base Ball Club formed in 1866 and fielded competitive teams in the National Association of Base Ball Players (NABBP) 1867 to 1870, a time of a transition that ambitious Cincinnati, Ohio businessmen and English-born ballplayer Harry Wright shaped as much as anyone. Major League Baseball recognized those events officially by sponsoring a centennial of professional baseball in 1969.
Thanks partly to their on-field success and the continental scope of their tours, the Red Stockings established styles in team uniforms and team nicknames that have some currency even in the 21st century. They also established a particular color, red, as the color of Cincinnati, and they provide the ultimate origin for the use of "Red Sox" in Boston.
Below is an image of the 1869 Cinncinati Red Stockings.