Every seat in the old-fashioned, wooden-galleried church was taken. Every city politician who wasn't dead (in the polls) was there or sent a representative. Marion Barry said via letter that the pastor "stands tall as a Cedar of Lebanon," which was something of an understatement, but this being Saturday before the primary, Barry was probably a little pressed for literary time. The architect, the contractor, the bank representative and the proprietor of the O Street Market -- all of whom addressed the congregation -- mixed in with the parishioners who joyfully jammed the 1,200-seat capacity of Shiloh Baptish Church, which resembled an overflowing bandwagon.

Little girls in Argo starched dresses, third-generation members flipping paper fans, ushers in white suits with pa;e pink shirts and white ties and medallions -- everybody had come of the bandwagon which Shiloh's pastor, the Rev. Henry C. Gregory III, had quietly gotten rolling in 1977. He had had a "vision." Saturday that vision -- a Family Life Center -- had come to pass.

Gregory is a quiet and soft-spoken leader. He compels with faith more than fireworks, which is consistent with the tradition of Shiloh. But on Saturday Shiloh could barely contain itself.

"We did it!" proclaimed 88-year-old parishioner Josephine Carole Smith from the pulpit. The congregation roared with approval at this simple statement of a complex fact. After the services, Gregory snipped the red ribbons and opened the doors of the $5.5 million center -- a six-level, multipurpose building at Ninth and P streets NW in the middle of a black, poor, sociologically splintered neighborhood where Shiloh sits.

"With God all things are possible," piped the Children's Choir toward the end of the service. But without any government funding, or bone-crushing loans? Yes. Shiloh has a tradition of doing without and getting further. And Gregory (a Howard, Harvard and Cambridge graduate) is part of an unbroken line of Shiloh Ministers who have gone about the Lord's business with an effectiveness that makes Riggs National Bank (its principal lender) look slatternly by comparison.

"We have a $3.7 million loan for 25 years with Riggs," said Monteria Ivey Sr., chairman of the board of the new Family Life Center, "but we plan to retire that loan in three years." The way Ivey sees it, there isn't a whole lot of sense in letting a loan drag on.

The church ceremony that preceded the ribbon cutting was rich with preachers and parishioners who stole and re-stole the show from each other.

"Shiloh has the reputation of being the strangers' home," said the Rev. Kenneth Burke Jr., a white minister who formerly served there. "But where are the strangers?" Everybody roared. They knew what he meant.

"We can truthfully say that God is real because He has brought us a mighty long way," said Euna Smith of the Expansion Committee. "We have come this far in faith and we are in deep waters now. I ask God not to fail us now." Everybody laughed and knew what Smith meant, too.

"If . . . it . . . had! not! been! . . . for . . . the . . . Lord! at! my side! Where would I be?" thundered the Lofton Volunteer Chorus. The Senior Choir sang the Beethoven "Ode to Joy" hymn as the congregation flowed out into the sunshine and ceremony.

Walter Fauntroy, who had just whipped everybody up into euphoria inside with his "We're cutting out Reagan's foolishness and cutting in the Lord" speech, was one of the dignitaries who stood by Gregory as the ribbon was snipped. Fauntroy checked his watch only once. A large "Fauntroy for Delegate" truck with loudspeakers was parked outside the church. Balloons and a campaign slogan, "Save our children now or there will be no future tomorrow," were plastered over the sides.

"My grandfather," said Josephine Carole Smith, "came up here with the original group of 21 freed slaves. What I like about this church is that we're not satisfied to just be on a corner. We want to reach out and touch people. The building isn't the end of anything. It's just a sign of something."

The heart of Shiloh Baptist's membership is large, multichambered and loyal. Founded in 1863 by 21 ex-slaves from Fredericksburg, Va., it now has more than 5,000 members, 90 separate community services (from drug addiction counseling to a notary public) and 10 full-fleged choirs that drench the Sunday services with music so magisterial and toe-tapping that on most Sundays mighty Shiloh doesn't have enough room for itself. If one doesn't get there by 10;45 for the 11 o'clock service, you have to go to the basement and watch it on television. "It's a large church," said one parishioner, "but it's warm."

Shiloh is also a rich church. Its members tithe, with some donating more than the customary 10 percent (after taxes); and many gave still more for the Family Life Center, one woman contributing $100,000 and several others $10,000. Even the building contractor, who had cost overruns, came through with a $10,000 check after the center opened.

Shiloh exerts a rather inspired, low-key pressure on those it comes in contact with, and while more than one third of its parishioners have prospered and moved away from the Ninth and P streets corner where the church sits, they return weekly to the old neighborhood, over which Shiloh casts a long shadow. And when Gregory snipped the ceremonial ribbon of the new Family Life Center next to the church, Shiloh's shadow was "bright shining as the sun."

The modern building, designed by Howard University graduate Robert Nash, has six levels, with something for everybody. There is the "Tuning Fork Eatery" open to the public, a basketball court, jogging track, racquetball-squash courts, video games, a sauna and Jacuzzi. A 600-person banquet hall with plush red carpets and white, red-flower-sprigged wallpaper can be rented out for large events; so can a rooftop garden with Astroturf and real flowers in windowboxes. One entire floor is devoted to various sized rooms -- all elegantly furnished -- for conferences, workshops and even a "Fashion, Fun and Fads" boutique. All 65,000 square feet of the brick and plate glass building (with innovative features such as recessed skylights in the offices for plants to hang) are carpeted, or furnished in modern, comfortable chairs and tables. Once in the building, it becomes difficult to think of a reason to leave. The surrounding neighborhood is crashingly bleak, yet it is precisely because of the neighborhood that Gregory decided that something unbleak was due.

Gregory looks upon mountains the way other people view molehills. What tension he may feel is either in the hands of the Lord or concentrated in one small dimple on his forehead. When prodded about his "vision," he said he simply felt called to do something about the black family, which needed a place where it could rejuvenate itself. While the Family Life Center is emphatically open to anyone in the city, it is the black family -- torn, splintered and divided against itself -- that Gregory was determined to serve. A general membership costs $50. One hundred dollars gives you the sports facilities as well. There is a flexible payment plan and even a scholarship fund. Anybody who really wants to belong can. The center is holistically designed.

"Even the church can be divisive," said Gregory. "I remember as a young person all the hours I used to spend waiting for my father, who was also a minister, on a park bench across from his church. The basic units in our society are the family and the religious institutions. We have the problem of unemployment. But there is also the problem of physical fitness, so a man or woman can hold a job. The Family Center hopes to foster practical wisdom. Then there is the third area, of value clarification. The center will foster -- through different kinds of education workshops -- the ideas of honesty, industry, dependability, and sensitivity to others."

Wasting no time, the center is holding its first conference, "Building Foundations: Centering on the Strengths of Families," this week. Co-sponsored by Howard University and the District of Columbia Department of Human Services, speakers such as Mayor Barry, Marian Wright Edelman, the Rev. Jesse Jackson and Dorothy Height, president of the National Council of Negro Women, will take part.

At the kick-off banquet Saturday evening, actor Ossie Davis and his wife, Ruby Dee, read from the works of black poet Langston Hughes. "What happens to a dream deferred?" he intoned before the 600 banquet quests, who sat at tables bright with candles, glass goblets and food. "Does it dry like a raisin in the sun?"

For Shiloh, for the moment, the question was moot.

"We are each other's harvest," recited Dee, reading from the poetry of Gwendolyn Brooks. "We are each other's business . . . magnitude . . . and bond."