The president and Mrs. Reagan began a marathon of ball-going last night with a visit to the American Legion's banquet in a capital celebrating both the inauguration and the hostages' freedom.

"there are no celebrities here," said one Inaugural Committee staff member. "Just Liz."

While other ballgoers around town were treated to views of Cabinet members and other Washington-style celebrities,those who went to the Air and Space Museum had only Elizabeth Taylor Warner to gawk at until late in the evening.

And Liz certainly was something to look at. Wearing a navy chiffon gown with a multicolored sequin bodice, she displayed a wide belt around a trim waist, and diamonds in her ears, and around her wrists. "I'm so glad she looks so beautiful," said one gawker.

Mrs. Warner occasionally played emcee; she introduced singer Robert Goulet, as people from Virginia, Iowa, Ohio, Delaware and the state of Washington danced the fox trot or a sedate jitterbug under hanging airplanes and mounted space capsules.

Mrs. Warner was supposed to interview Gov. John Dalton of Virginia and Sen. Barry Goldwater (R-Ariz.) for the viewers of the satellite telecast the Inaugural Committee had arranged for closed-circuit viewing in about 80 cities. But the program seemed to be fairly uncertain. "She doesn't want todo it," said one source. "She wants John to do it."

When Vice President George Bush arrived with his wife, who wore a bright blue satin dress, the crowd crushed forward like lemmings to listen to him say how pleased he was about just everything. As he left, the band, for some reason, struck up a square dance. Liz and Dalton's wife Eddy obliged the crowd with a little do-si-do on stage and jigged their way off.

"she knows how to give them what theywant," said one ovserver.

President Reagan visited the ball at 11:30 p.m., greeting the enthusiastic crowd and saying, "You reinforce my ownbelief in my own words more and more. . .that together we're going to dowhat needs to be done."

Referring to the satellite balls, he said that it was "symbolic that they were raising money for charity. Here we are on the first night, and there are communities that are keeping their money at home." And the crowd roared.

Leaving the stage, the president obliged photographers by having his picture taked against the backdrop of the Wright Brothers biplane hanging from the ceiling. Then he turned back to the crowd. "No matter what they say, it isn't true that I flew that."