The U.S. Senior Open is one of the major championships in men's senior golf. It was first played in 1980 and is administered by the United States Golf Association (USGA) and is recognized as a major championship by both the Champions Tour and the European Seniors Tour. Initially the lower age limit was 55, but it is now 50, which is the standard limit for men's senior professional golf tournaments. The event is open to amateurs but it is dominated by professionals.