Behind the badge: Start your engines
26 professional and 16 amateur -- will compete in the tournament as it kicks off in June. After 40 teams participated in the prestigious tournament in 2004, two Major League Soccer expansion teams have been added to the fray this year, bringing the total number of teams to its highest level since MLS began participating in the event in 1996. The U.S. Open Cup, which is recognized as U.S. Soccer's national championship, is an annual competition open to all amateur and professional soccer teams affiliated with U.S. Soccer. United captured the tournament title in 1996.