Elizabeth A. Belzer bounded off a blue-carpeted stage today and brought an era that spanned 135 years from steam ships to nuclear engines to an exuberant end.

The dark-haired 21-year-old from Westminster, Md., held her diploma aloft clasped it to her chest and then put her hand to her mouth to cover an ear-to-ear grin. She had just become the first woman graduate of the United States Naval Academy.

Belzer was the first of 55 female and nearly 900 male midshipmen who graduated in commencement ceremonies held under a sunny and blue sky in the Navy-Marine Corps of Memorial Stadium before more than 15,000 people.

But on this day of momentous departure from tradition, it was the links with the past that were underscored by regalia-laden admirals and many of the graduates themselves.

"Some of you are puzzling why I haven't made a big thing about this being the first class ever to count women among its graduates," said Adm. Thomas B. Hayward, chief of naval operations, in his address to the 36 companies of midshipmen seated before him in summer white uniforms. "It seems to me it's about time we stop making firsts out of these young women. I am confident they're tired of it. They have met the test . . . They have earned just as smart a salute and just as much respect as any other graduate."

These remarks in a 20-minute speech that invoked the virtues of sacrifice, guts and Calvin Coolidge's homily on persistence, drew the loudest applause.

As they did during their Plebe Summer four years ago, the pathbreaking class of 1980 had to contend once more with a bane of existence most midshipmen are spared -- the press, which was in battalion strength with more than 60 reporters and television crews documenting every squeal, tear and sigh.

There was no shortage of jubilation on the field up to the stage at midfield.They slapped hands, whooped and sprang into the air, holding the blue folio diplomas aloft like trophies as howls of congratulations came from proud parents and underclassmen in the stands.

When it was over, 938 men and women newly sworn into the Marines as second lieutenants and into the Navy as ensigns plucked their shoulder boards off, grabbed their hats and hurled them into the air again and again in a great fountain of flying headgear that came down like hail and sent the camera crews ducking for cover. Children darted out of the stands hoping for souvenirs.

Few mids begrudged interviews.

"I'm walking on water," cried Roosevelt Johnson of New Orleans. "Throwing that hat sure felt good."

All around him on the field, cameras flashed, parents beamed and midshipmen radiated a sense of jubilation and relief that in part was a measure of the four year ordeal they had just completed.

"I had two sons and one daughter, and it was the daughter who went to the Academy," said retired Navy captain Arthur Ray Hawkins, fastening a button on his own uniform as he gazed at the new ensign in his family -- 22-year-old Jill.

"Hey, that looks pretty god on you," Jill said.

"The old man's is pretty good shape," Hawkins said, climbing up on the ramp to the podium where a long receiving line had been formed by graduates and families waiting to greet the brass.

Over by the bandstand, Lt. Col. Albert Allen of Lumberton, Tex., was pinning gold bars on his son Travis while Evelyn Allen watched.

"A lot of pressure was released Travis said.

"Three-quarters of an inch from the seam," his father said. "That's where the bars go."

Travis, like the 155 other graduates headed for the Marines, had already had his hair trimmed down to the skin-headed "regs."

"It's an occupational hazard," he said. The only thing he regrets about being in the first class with women is the "second-hand treatment" he got the first day. "This television reporter came up and said, 'Excuse me, would you mind getting out of the way so I can interview. this woman.'"

"If his father survived 20 years in the Marines I imagine Travis can," said Evelyn Allen. "We don't have any sissies in our family.

New white uniforms were unpacked on the field which turned into a giant alfresco dressing room as new officers changed into fresh "blouses" and new hats and shoulder boards. Mids-kissed, which was something new. Parents kissed, which wasn't Lt. Arcello Josiah, 22, lipstick all over his new Marine uniform. One woman found a jettisoned cap with a picture of Bo Derek pasted inside. Under-classmen combed the field hoping to be the first to salute the new officers, which by tradition entitles them to a silver dollar.

Practically everyone had relaxed except Ensign Pam Wacek, 21, from Oak Forest, Ill. "I'm still nervous," she said. "I'm getting married tomorrow."