In the outer suburbs of Washington, long filled with Christian churches, new and expanding Muslim mosques are changing the religious landscape.

In Woodbridge, a $1.8 million mosque built to hold 1,000 worshipers will open in January. Starting in October, Ellicott City Muslims will pray in a new $2 million mosque large enough to accommodate almost 1,000 people. Mosques from Annapolis to Manassas are growing as Muslims who have migrated to the outer suburbs seek places to worship near where they live.

Some are moving into office buildings and homes -- even into some former churches -- as Muslims establish informal houses of worship called masjids. Close-by mosques are desirable for the Muslim faithful because of the religion's ritual of five daily prayers and Friday prayer services.

"It is difficult to commute for the prayers," said Farzad Darui, manager of the 48-year-old Islamic Center of Washington, the first mosque in the area built from the ground up.

The boom in exurban mosques has resulted from the migration of Muslims to the outer suburbs, as followers of Islam -- just like other suburban emigrants -- seek less-expensive housing and good schools.

"Like all other segments of society, there's a move to suburbia, and Muslims are part of that movement," said Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations, based in Washington.

As those Muslims establish more mosques, more Muslims are drawn to the area. About 300,000 Muslims live in the region that stretches from Richmond to Baltimore, according to Islamic organizations. In metropolitan Washington, the number of suburban residents who claimed ancestry from a mostly Muslim country jumped 81 percent from 54,295 in 1990 to 98,084 in 2000, according to a 2003 study by the American Communities Project, a Brown University project on population trends.

In the post-Sept. 11 world, it hasn't always been easy to incorporate new mosques into suburbia. In some places, neighbors have been less than welcoming, even suspicious of who might be inside praying. Vandals have set fire to a mosque sign and spray-painted derogatory words on buildings and a van owned by the All Dulles Area Muslim Society in Sterling, which with 5,000 congregants is one of the largest mosques in the area.

In Howard County, there have been verbal attacks on Muslim women for their covered heads.

But local Muslim leaders downplay such incidents as isolated. Dulles Imam Mohamed Magid Ali said his congregation has successfully reached out to the community through open houses and interfaith events that foster understanding and tolerance.

For decades, the Islamic Center of Washington, with its distinctive 160-foot minaret on Massachusetts Avenue, was the center of Muslim worship in the region. But in the early 1980s, a group of mostly Arab college students moved out of the District to establish Dar Al Hijrah in Falls Church, said Imam Johari Abdul-Malik, also the mosque's director of outreach programs.

By the early 1990s, immigrants as well as African American Muslims and a second generation of Muslims, began trickling into the outer suburbs.

The new Woodbridge mosque, Dar-Alnoor, is a testament to the explosion of the Muslim population there, said Adil Khan, a spokesman for the Muslim Association of Virginia, a group of Woodbridge Muslims. After Spanish, languages of Muslim-dominated countries -- Erdu, Arabic and Farsi -- are the fastest-growing languages spoken at home by Prince William County students.

When Adil Khan was in high school in Prince William in the 1990s, he and a handful of other students formed a Muslim student association.

"There were, maybe, five of us," he said. "Now they have clubs with 30 to 40 members at Forest Park and Hylton [high schools]. Literally, it's leaps and bounds."

The Muslim Association of Virginia began worshiping in homes in 1988. Five years later, it turned a dilapidated, one-story house in the woods off Route 234 into a masjid. Dar-Assalaam looks like any other old house on the side of a country road, except for a sign written in Arabic and dozens of cars that squeeze into a gravel parking lot for Friday prayer services. Inside, congregants can cleanse themselves in a makeshift shower before praying in a room with a teal and beige striped carpet angled to face Mecca. In a corner of the room, women worship separately from men, divided by a sheet draped between two partitions.

The accommodations are not ideal. The women should have their own room in which to worship, mosque leaders say. The children attend Sunday school in rented classrooms at a high school.

"This year, we're bigger than before," Amal Muhammed, 36, said after a recent prayer service. "It's too small here. We need a bigger place."

After Dar-Alnoor, the new mosque, opens in January a few miles away, Dar-Assalaam will remain open, just to give the congregation further room to grow.

During a Friday prayer service at Dar-Assalaam, a few women sold boxed lunches for $5 while two men peddled $35 tickets to a dinner at an Alexandria hotel. Attendees pulled out checkbooks and cash to raise money for Dar-Alnoor.

Constructing a mosque, even in a burgeoning Muslim community, is no easy matter.

Because Islam outlaws borrowing money at interest, Muslim leaders said, congregations can't rely on bank loans to pay construction costs. Instead, they rely on fundraisers for the millions of dollars needed for their houses of worship. For that reason, it takes about seven to 10 years to build a mosque, local imams said.

It has taken the Woodbridge congregation even longer: 12 years, Rafi Ahmed, president of the group, said.

Everyone donates, spurred by the Islamic doctrine, "Anybody who builds a house for Allah in this life, Allah will build a house like it in paradise," said Dar Al Hijrah's Abdul-Malik, who also serves as chairman of the Coordinating Council of Muslim Organizations, a regional group that represents 40 mosques.

Organizers of Dar Al-Taqwa, the Ellicott City mosque being built to accommodate an overflowing Muslim community, kept down costs for the $2 million building by using Muslim engineers and a contracting firm that volunteered its time and services, said Imam Mahmoud Abdel-Hady. Nevertheless, he said, the money had to come from Muslims in the area.

Building suburban mosques has also faced special challenges since the Sept. 11, 2001, terrorist attacks and other incidents of terrorism in Europe, Africa and elsewhere.

Area mosques have tried to educate non-Muslims that extremist views are not a part of the religion of Islam. After the recent bombings in London and Egypt, the Woodbridge mosque and a mosque in Manassas jointly issued a statement condemning the incidents. "These actions are not sanctioned, nor justified, in Islam," the statement read. Both mosques promised to nurture "interfaith understanding and diversity" in Prince William.

Yet connections between mosques and more militant elements of Islam have been unsettling for some members of the public. The FBI found that two of the Sept. 11 hijackers worshiped at Dar Al Hijrah in Falls Church for a short time. And Ali Al-Timimi, a popular lecturer at the Center for Islamic Information and Education in Falls Church, was recently sentenced to life in prison for inciting a group of followers to train for a violent jihad against the United States. The executive committee at Dar Al Hijrah supported him and called the federal prosecution overzealous.

In the Chicago suburbs, residents and public officials have used zoning laws and traffic concerns to fight proposed mosques, said Abdul-Malik, who traveled to Illinois to work with one of the new mosques.

"Their problem is not saving money [to build the mosque]. It's getting a permit," he said.

A diverse population and outreach groups have helped quell uneasiness in Northern Virginia, said John Steinbach, chairman of Unity in the Community, a Prince William interfaith group founded in 1996 after several racist incidents.

Still, suburban mosques in the Washington area tend to make a major concession to non-Muslim neighbors: eliminating the traditional Adhan, or call to prayer, which is usually chanted in Arabic outdoors over a loudspeaker.

"It was part of the agreement. No noise," said Abdul-Malik.

Abdul-Malik said he hopes that mosques become as much of a part of the suburban fabric as churches. It would be nice if suburban Muslims could hear the call for prayer just as they do on Massachusetts Avenue in Washington, he said.

"I'm laughing now," he said, speaking from a coffee shop near his office in Falls Church as noontime chimes began ringing at a nearby church. "I can hear the church bells coming from Columbia Pike. . . . One day we will hear bells and the call for prayers. I believe that day is coming."

Dar-Assalaam of Woodbridge is a cramped, converted house. A large new mosque will open in January.Dar-Alnoor, the new mosque, will accommodate 1,000 worshipers. Construction has taken 12 years.