This year's field is expected to be the third largest with 16,638 entries. The field size limit was reduced from 20,000 for last year's race, which finished with a field of 17,813. The record field was in 1996 with 38,708.
The last American runner to win was Lisa Larsen-Weidenbach, who ran away from the field in 1985. The last US male runner to win was Greg Meyer in 1983.
Prize money was awarded for the first time in 1986 thanks to the support of John Hancock. Rob de Castella of Australia earned $60,000 and a Mercedes-Benz for his victory.
Security will be increased this year with 1,500 police and three state police helicopters guarding the course along with 415 National Guard troops and another 1,500 security personnel.
Women's numbers are up. The number of women competing in the Marathon has risen steadily since women became official participants in 1972. That year there were eight starters and eight finishers. This year there are 6,273 women entrants (who make up 37.7 percent of the field).