More than 25,000 black Americans declared their own holiday in Washington yesterday.

Led by the charismatic musician, Stevie Wonder, they reported for a rally at the Washington Monument, instead of work or school, in a national call to make the late Rev. Martin Luther King's birthday a legal holiday.

The occasion was high-spirited, with the slain civil rights leader's son, Martin Luther King III, delivering stirring oratory in his father's name.

"My daddy had a speech where he asked, 'How long, Lord?' And the answer would be, 'Not long,'" said King. "Now i'm asking, how long, Lord, will it be before we get a holiday? Not long. No lie can live forever."

The mostly black crowd erupted into applause. On stage, civil rights activists -- Ben Chavis, Dick Gregory and D.C. Mayor Marion Barry among them -- nodded and stroked their chins. "Just like his daddy," some whispered.

The icy cold weather, which included about an inch of new snow, apparently did not deter the crowd, the largest gathering of blacks in Washington since African Liberation Day in 1973. Estimates on crowd size, however, varied dramatically, with U.S. Park Police claiming there were 15,000 participants. Other observers said the the crowd numbered at least 25,000 but not the 200,000 claimed by the event's sponsors.

Activist-comedian Gregory, predicting disagreement on the crowd size, drew applause when he looked out over the Monument grounds and said there were "googobs of Blacks out here."

Earlier in the day, about 3,000 persons, including Wonder, marched on Martin Luther King Avenue in Anacostia's third annual Martin Luther Kings Day parade in Southeast Washington. About 500 others gathered at the Martin Luther King Jr. Memorial Library for the District of Columbia's official progam honoring King, who would have been 52 yesterday.

Barry, the main speaker at the library, praised King as the "leader of the greates social movement of our time." He called for a legalized holiday, but also used the occasion to criticize media coverage of his administration.

If King were alive, he said, "he would ask what it is inside of us that makes us want to fight all the time, to find fault where there's none to be found. Why is it that the media has to always report the negative, what is wrong, what's not happening as opposed to what is happening. If we're not careful and we try to bring one person down, we can bring our whole city down."

Later, when he was being intoduced as a speaker at the rally, the mayor was loudly booed.

By the contrast, the crowed was estatic over Wonder, who called the occasion one of the happiest days of his life.

"You have made me so very happy," said Wonder, whose idea it was to have a march and rally and pay for it with a benefit concert at the Capital Centre tonight. "All of us who believe so deeply in the dream know that you believe too."

Noted for his singing -- not speaking -- Wonder, 30, launched into a song called "Happy Birthday" from his latest album. It is an upbeat and bouyant call for making King's birthday a national holiday.

At a press conference later, Wonder said, "I think that the artists have been the catalyst for expressing social conditions since the beginning of all time. I think that we as artists are committed to creating positive things for people to hear in songs . . . I am not a politician. I am not a leader. I am a human being given the honor and gift of song and with it, I give the best possible."

D.C. Del. Walter E. Fauntroy, newly elected chairman of the Congressional Black Caucus and a long-time colleague of King, was the master of ceremonies at the rally and walked the parade route from the Capitol to the Monument. Ofiedld Dukes, a Washington-based public relations specialist organized the rally at Wonder's request.

Participants came from as far away as California and Oregon, many bringing with them petitions containing thousands of names to be presented to Congress. Meanwhile, Sen. Charles McC. Mathias (R-Md.) introduced legislation in the Senate yesterday to make King's birthday a holiday. A similar bill has been introduced each year since King was assassinated in 1968, but it has failed each time.

"I feel that it's time for black folk to get off the dime and start moving somewhere," said Sandra Washington, a secretary from San Diego who flew to Washington for the occasion. "I think people are feeling that we aren't going much farther, so we better start fighting to keep what we got."

Rubin Ward, a barber from Chicago, closed his shop and caught a bus to Washington for the rally. "You got the KKK (Ku Klux Klan) on the comeback on Reagan's coattails. Need I say more?"

Herman Edwards, a housing inspector from Houston, said the last time he was in Washington was for the March on Washington in 1963.

"I feel like old times, but mainly I'm here to hear Stevie Wonder. Now here's a guy who seems to know how to get things done. I mean, at least he knows how to get people to move."

Among the many chants shouted throughout the day was one that went, "Ain't nobody gonna turn me around," in which the names Ronald Reagan, Sen. Strom Thurmond (R-S.C.), chairman of the Senate Judiciary Committee, and the KKK were substituted for "nobody".