The United States is a country that joined IMO relatively late, and 1974 began to join IMO. However, in the United States, math competitions have a very long history. As early as 1938, there was a mathematics competition for college students in the United States-Putnam Mathematics Competition. The American Middle School Mathematics Competition (AHSME for short) began at 1950. Many countries, including China, participated in the competition. Starting from 1983, the American Mathematics Invitational Tournament (AIME) will be held. Winners of AIME can participate in the American Mathematical Olympiad (USAMO)( 1972). About 20 players with the best performance in USAMO will receive another three weeks of training, and six students will be selected as members of the American team.