There is no definitive answer to this question as it largely depends on how one defines a â€œprofessional sports teamâ€. For the purposes of this answer, we will assume that a professional sports team is any team that competes in a major league or similar top-level competition. With that definition in mind, the smallest city with a professional sports team is Green Bay, Wisconsin, home of the NFLâ€™s Green Bay Packers.
With a population of just over 104,000 people, Green Bay is by far the smallest city in the United States with a professional sports franchise. The next smallest city with a professional sports team is Buffalo, New York, which has a population of just over 262,000 people. That means that there are nearly 158,000 more people living in Buffalo than there are living in Green Bay.
Interestingly enough, though they are not technically considered to be part of the same city (Green Bay proper), there are also two other small towns located within close proximity to each other that have professional sports teams: Ashwaubenon and De Pere. Combined, these two towns have a population of just over 26,000 people â€“ meaning that there are actually more people living in these two small towns than there are living in Green Bay itself!