Shhh! St. Ignatius Roman Catholic Church in Oxon Hill has a secret. It's 150 years old this year.

That's a milestone by any measure, but no one is shouting the news from the 80-foot-high steeple-top. There will be a parish dinner in September, but no Roman Catholic church luminaries are expected to attend, and there will be no proclamations from the governor or county executive.

"There's too much image stuff in the world," said the Rev. Mark F. Hughes, the church's pastor since 1992 and one of three priests and four nuns serving the parish, which takes in Oxon Hill and Fort Washington. "The sense of the parish is to keep it a parish event. We decided to keep it low-key."

None of which is to suggest that the anniversary is not a big deal among the 300 families in the parish, which has changed over the years along with Prince George's County. "It's a beautiful church," said Ethel Hands, head of the 32-member parish unit of the Ladies of Charity, which works with the poor. "It has a lot of history."

Among those who helped raise money to buy the land was Mary Elizabeth Eugenia Jenkins Surratt. She is better known simply as Mary Surratt, the woman who was hanged as a conspirator in the Lincoln assassination. Her mother is buried in the St. Ignatius Cemetery, where the earliest marked grave dates to 1853.

"Inscribed in your parish annals," Cardinal James A. Hickey wrote in a letter to Hughes in June, "are names like Edelen, Spaulding and Surratt--families steeped in Maryland history." Other once-prominent local names include Mattingly, Brooke, Fowler, Sheriff and Swann.

Before the Civil War, slaves sat in the side galleries of the original church, replaced in 1890 by the current structure, whose interior has just undergone a $60,000 sprucing-up. The sanctuary has 13 pews and 20 stained-glass windows, donated by parishioners and priests during the late 19th century.

Segregated seating at St. Ignatius continued until after World War II. But today, the parish is happily multicultural, by all accounts, with whites constituting about half the congregation, and Filipinos and African Americans 25 percent each.

"I still venture back, because it's just part of my heritage, my family," said Mary Glenn Lincoln, 30, an African American woman who lives in a neighboring parish but whose father, a retired Air Force officer, is still active in St. Ignatius. "I got married in that church, received all my sacraments in that church. The priests are just wonderful."

Filipino American Leticia Lechoco, a member since 1973 whose husband is chairman of the parish council, agreed. "I love that church," she said. "I've been a beneficiary of the love and support of the members, during a time years ago when I was in need."

Adult education classes at St. Ignatius are "a good mix" of all ethnic groups, said parishioner Don Horn, a physicist at the Naval Research Laboratory who joined the parish in 1962 when he moved to Fort Washington and is a regular participant.

But most of the active adults are older. "The whole demographics of the area have changed greatly," Horn said. Many in the younger generation have moved away, to places such as Woodbridge and Waldorf.

Horn is optimistic, however. "I think we have a good nucleus of people now," he said. "These things run in cycles. I expect an influx of young people in the next 10 or 15 years. It's a very vibrant parish."

Among the younger parishioners is Derrick Christopher Delmore, 20, of Fort Washington, a Stanford University student who in 1998 became the World Junior Champion in men's figure skating.

Adjoining the church is a Catholic school, which opened in 1966. It has kindergarten through grade 8 and last spring had 228 students, about 60 percent of them non-Catholic and 75 percent African American. The 11 teachers and principal are lay people. In addition, Hughes instructs the students in religion.

"It's a typical Catholic school," he said, although, like many these days, it no longer attracts a majority of Catholic students. Parents pay tuition of $3,000, or $4,500 for two students.

St. Ignatius used to offer summer school, but not this year. The other day, Hughes opened the church office door to the outside only to confront a woman whose arm was raised to knock. "I came to see God," she said. "Does He enter that quick?" She had come to inquire about day care, which is offered only during the school year.

Year-round there are daily masses, including three on Sunday, confessions on Saturday and baptisms by appointment. The church sits on 14 acres fronting on Brinkley Road and adjoining a horse farm not far from Rosecroft Raceway.

"Every once in a while, the horses come through and eat the grass in the cemetery, so we have to chase them back home," the pastor said.

The parish council's decision to have a low-key anniversary was "unanimous," Hughes said. The celebration will culminate with the dinner Sept. 25. It will be at a nearby Knights of Columbus Hall, which holds about 300 people.

"That was another thing," he said. "We could've driven around the Beltway, got one of those big halls, but . . . no."

Demographic changes in the immediate area in the 1990s have brought about a decline in active membership, from 1,200 to 700 people, according to Hughes, as older people have retired and moved away, to be replaced largely by newcomers of other faiths.

Nonetheless, Hughes said, the parish has "stabilized and started to increase gradually." It is a matter of faith with him that St. Ignatius will be about 50 years hence, for its bicentennial. "No question," he said.