Final answer:
The first professional league in sports was the National Association of Professional Base Ball Players, formed in 1871 and lasting until 1875.
Step-by-step explanation:
The first professional league was the National Association of Professional Base Ball Players, formed in 1871. It lasted until 1875.
The National Association faced various challenges, including financial instability, gambling issues, and concerns about the quality of play. In 1876, it was replaced by the National League of Professional Baseball Clubs (often referred to as the National League or NL), which became the first enduring major professional baseball league. The National League is still in operation today, making it the oldest extant major professional sports league in the United States.