In 2010, it split into the USAMO and the United States of America Junior Mathematical Olympiad (USAJMO).
In order to be eligible to take the USAMO, a participant must be either a U.S. citizen or a legal resident of the United States or Canada.
[4] In addition, all participants, regardless of geographic location, must meet qualification indices determined by previous rounds of the AMC contests.
The USAMO was created in 1972 at the initiative of Nura D. Turner and Samuel L. Greitzer,[5][6][7] and served as the next round to the AHSME until 1982.
In 1983, the American Invitational Mathematics Examination was introduced as a bridge between the AHSME and USAMO.
[8] The USAMO (and the USAJMO since 2010) is restricted to approximately 500 (250 prior to 2006) participants combined each year.
To keep this quota constant, the AMC Committee uses a selection process, which has seen a number of revisions in the competition's history.
Cutoffs, based on AMC 12 indices, are determined so that approximately 260-270 students qualify for the USAMO.
Cutoffs, based on AMC 10 indices, are determined so that approximately 230-240 students qualify for the USAJMO.
U.S. citizens and students residing in the United States and Canada (with qualifying scores) are eligible to take the USAMO and USAJMO.
The approximately 230-240 individual students with the top AMC 10 based USAMO indices will be invited to take the USAJMO.
The USA Mathematical Olympiad will be administered to approximately 270 students, mostly selected from top ranking AMC12 participants.
5.In order to find unrecognized young talent, AMC 10 takers who score 11 or more on the AIME will be invited to the USAMO.
The second selection of approximately 160 USAMO participants will be among students in the 10th grade and below who received an AIME score at least as high as the floor value.
Since 2002, the USAMO has been a six-question, nine-hour mathematical proof competition spread out over two days.
Each question is graded on a scale from 0 to 7, with a score of 7 representing a proof that is mathematically sound.
The number of perfect papers each year has varied depending on test difficulty.
Prior to 2002, the problems were mailed to the schools in sealed envelopes, not to be opened before the appointed time on the test day.
Student responses are then faxed back to the AMC office at the end of the testing period.
In 2002, the Akamai Foundation, as a major sponsor of the American Mathematics Competitions, invited all USAMO participants to take the test at a central event at MIT in Cambridge, Massachusetts, all expenses paid.
Top USAMO and USAJMO participants are selected to MOP through multiple criteria of entry.