Major League Soccer is the premier soccer league in the United States. As of its upcoming 2021 season, MLS has 27 clubs (24 from the U.S. and 3 from Canada). The league plans to expand to 28 teams in 2022 and 30 in 2023. The 34-game schedule runs from mid-March to late October, with the playoffs and championship in November. Soccer-specific stadiums continue to be built for MLS teams around the country, both because football stadiums are considered to have excessive capacity, and because teams profit from operating their stadiums. With an average attendance of over 21,000 per game, MLS has the third-highest average attendance of any sports league in the U.S. after the National Football League (NFL) and Major League Baseball (MLB), and is the ninth-highest attended professional soccer league worldwide. Other professional men's soccer leagues in the U.S. include the current second division, the USL Championship (USLC) and the third-level USL League One (USL1), which launched in 2019 under the auspices of the USLC's operator, the United Soccer League. Another competition, the second North American Soccer League, had been the second-level league until being demoted in 2018 due to instability, and soon effectively folded. The USL organization now has a formal relationship with MLS, and a number of its teams (both in the Championship and League One) are either owned by or affiliated with MLS sides.