FOR WEST POINTERS, IT IS THE training run from hell. The summer after their plebe year, cadets don full combat gear—including a 30-pound pack—then race, platoon against platoon, along an exhausting three-mile course. Four years ago, about a mile into the race, second-year cadet Rebecca Elizabeth Marier overtook a platoon-mate carrying two packs, his own and that of a teammate who couldn't keep up. Marier offered to take a pack from him. "At first he refused," she recalls, "but I insisted he give it to me. I wanted to be doing what the men were doing. I guess I was trying to prove something."

And that she did. On June 3—193 years after the academy was founded and 19 years after it began admitting females—Rebecca Marier, 21, became West Point's first woman to graduate at the top of the class. She beat out 858 men and 130 women—amassing a cumulative best in academics (she had a 3.95 average), military performance (field tactics and riflery) and physical fitness (she can do 100 sit-ups, 70 push-ups and run a 6-minute mile). "Rebecca's tougher mentally than other people," says Colin McGraw, 22, her cadet classmate and boyfriend. "She works to meet her own standards. She doesn't quit."

Marier is used to being No. 1. Reared in New Orleans, the daughter of Dr. Robert Marier, 51, associate dean of medicine at LSU Medical School and chief administrative officer at University Hospital, and his wife, Joanne, 49, a lawyer, Marier was a National Merit Scholar and president of the senior class at Metairie Park Country Day School. (Her younger sister Alicia, 19, is a Princeton junior.) Rebecca won varsity letters in volleyball, soccer and tennis. She applied to several top colleges and was accepted at Harvard but chose West Point, she says, because "I thought it would be good to learn to be a leader."

First, though, she wants to become a healer. This fall she will enter Harvard Medical School—the second West Pointer to do so. "I think I've changed a few people's minds about women in the military and in leadership positions," she says. "This is the '90s. People better get ready, because there are a lot of talented women behind me."