Ward 7, whose residents often call it the "forgotten" section of Washington, threw itself a party yesterday, a rollicking 30-block-long parade to celebrate the neighborhoods and families of the city's far eastern corner.

An estimated 3,000 people lined the three-mile parade route along East Capitol Street, Benning Road and Minnesota Avenue in far Northeast for the first Ward 7 Day parade, an extravaganza of some 85 marching units, including school bands, civic groups, businesses, antique cars, horses and politicians.

While others demonstrated in other parts of town over weightier matters--a crowd at Lafayette Square arguing for stronger U.S. support of Israel, a demonstration at the Organization of American States headquarters in support of Argentina's position on the Falkland Islands, a 7,000-strong walk-a-thon for the March of Dimes--the people of Ward 7 rallied simply in celebration of home.

"This is the biggest thing we've ever had out here, ever," said a delighted D.C. Council member H.R. Crawford (D-Ward 7), who proposed the parade after participating in Ward 8's annual rites in recent years.

"We are trying to emphasize that we are somebody," Crawford said, "There is a great deal of frustration, great deal of unemployment, and people are looking for something to identify with."

Ward 7, cut off from most of Washington by the Anacostia River, is a diverse mixture of the middle class and the poor. It has about 3,000 units of public housing, much of it deteriorated, but also has a backbone of thousands of well-kept middle-class homes on quiet tree-lined streets.

"We have a lot going for us out here," said Mary Jackson, 41, a lifelong Ward 7 resident and one of 15 volunteer parade organizers. "Today we're celebrating that. This kind of thing brings the community together, to show we've got strong families, and good relations with the police, and good things going on in our schools."

School bands, more than a dozen of them, were the main attraction of the day, with Ward 7's local favorite, H.D. Woodson High School, drawing cheers from the crowd for its crisp high-strutting style that earned the band a first place in a recent citywide competition.

The black-and-white-suited Woodson Warriors had the honored first spot, marching behind the parade queen, 18-year-old Asonja Bell, the 1982 Miss Woodson, who wore a tiara and rode atop a purple Corvette convertible.

Competition among the bands was evident. When bands from Cardozo, Anacostia, Dunbar and Ballou high schools marched by, some of the local youngsters inevitably taunted them with shouts, telling the visiting bands to go home and informing them that Woodson was "Number One."

"I wish more people knew what these bands are doing for young boys and girls," said Jackson. "I have two wonderful boys, and it's such a relief" to have them involved in wholesome activity.

Jackson, a Senate employe who lives on 49th Street SE, wore her yellow "Ward 7-H.R. Crawford" baseball cap and her white Woodson High School Band Boosters jacket. Jackson, president of the band boosters, said the volunteer group raises about $20,000 yearly for the band because the school system provides little funding.

Parents and children, some dressed for play and some still wearing Sunday finery, lined East Capitol Street to watch the slow-moving procession that took three hours to reach its destination of Kenilworth Park for opening day of the D.C. Sportsmen's League softball season.

"It's real nice to have something like this for the kids," said Brenda Shivers, 18, as she stood outside the drab East Capitol Dwellings housing project, holding her 16-month-old daughter Terrierica. "They should do this more often for kids. There's nowhere for them to play around here. The playground's all torn up."

Five blocks away, in front of the well-manicured lawns along East Capitol at 55th Street, Robert and Valeria Miller had just returned from Greater Mount Pisgah Baptist Church in Northeast and were standing with their daughter, Sherri, a Woodson graduate who is now a criminology major at the University of Maryland.

"Gorgeous," remarked Miller, as he watched the passing spectacle. "A lot of people never have the opportunity to really see this neighborhood. People just drive by East Capitol and they don't see how nice it is inside this neighborhood."

Further down the route, Frankie Barnes waited with his camera for nearly two hours beneath a flowering tree. Barnes, 42, a janitor at Fletcher-Johnson Junior High in Ward 7, was waiting to snap a picture of his school's marching band. "I'm gonna pin it up on the bulletin board," said Barnes, who has lived for 30 years in the ward. "I love it out here."

"This is an outstanding idea," said Raymond Hughes, a Secret Service employe who waited at Benning Road and 42nd Street NE to snap a picture of his daughter Sheray, in her purple-and-white colors of Kelly Miller Junior High, "but they should do it more often, not just in election year."

The only hitch came at about 4 p.m. when Crawford's shiny brown Mercedes, carrying the council member and his family at the head of the parade, unceremoniously quit--smack in the busy intersection of Minnesota and Nannie Helen Burroughs avenues.

A passing taxicab was flagged. Jumper cables were produced, but the shiny Mercedes refused to start. "The hell with it," Crawford finally said. "Get me a police car."

But just as the cruiser was being summoned, the Mercedes started up and the parade resumed. It was that kind of day for Ward 7.