They rose from their rows of white folding chairs overlooking the Potomac River while friends and family members waved miniature flags, hushed babies and held up phone cameras to record the moment.

Then they vowed to renounce allegiance to any foreign government, to support and defend the Constitution and laws of the United States and to bear arms on behalf of the country “when required by the law.”

“I take this obligation freely without any mental reservation or purpose of evasion; so help me God,” they said.

More than 100 immigrants took the final step toward becoming U.S. citizens during a special Independence Day ceremony at Mount Vernon by raising their right hands and taking the Oath of Allegiance to the United States.

For five men wearing dress blues, white hats and polished shoes, the oath followed a commitment they had already made to their adopted country when they enlisted in the U.S. Marine Corps.

Juan Cerda Guerra, 29, came to the United States from Mexico when he was 5 years old. He went to school in Minnesota, where his parents worked at a canned-food factory. He started his own family here. He has long felt like an American, he said Thursday.

“I just never had the title,” he said.

In nearly a decade of service to the Marines, including two tours in Iraq, he has held a number of ranks, including private, private first class, lance corporal, corporal and sergeant.

Now that he has earned his citizenship, he hopes that he can continue to rise in rank. “I’m already wearing the uniform,” he said.

“I’m willing to give the ultimate sacrifice, as they say.”

Non-citizens have served in the U.S. military for much of the country’s history. More than 660,000 military veterans became American citizens between 1862 and 2000, according to government statistics.

Since the attacks on Sept. 11, 2001, new policies were enacted to encourage more non-citizens here legally to enlist by expediting their citizenship process.

Nearly 90,000 members of the military have been naturalized since September 2002, many of them while stationed overseas.

This week, 7,800 new citizens are being naturalized in 100 scheduled ceremonies, including events designed specifically for members of the military at Bagram air base, Afghanistan; the U.S. Embassy in Seoul; and the Marine Corps Recruit Depot in San Diego, where nine recruits will be naturalized during basic training.

At the ceremony at George Washington’s estate in Virginia, Denis McDonough, the White House chief of staff, told the group that “America has benefited immensely from the contribution of immigrants and citizens like yourselves. We look forward to seeing what each of you writes into the next chapter of this great American story.”

A man dressed as Washington also congratulated the new Americans — 101 in all, from 46 countries — and volunteers from the Daughters of the American Revolution handed out red-tasseled programs to their friends and family members.

Tourists in sun hats and shorts watched and snapped pictures of the proceedings, which were held only steps from the front porch of Washington’s house.

Sandra Jones of Baytown, Tex., wore a blue T-shirt emblazoned with the letters “USA.” She said she got emotional watching the ceremony with the Marines in the front row. “It’s a privilege to be born here, but they chose to be here,” she said. “They chose to support this country before they had to.”

Ahmed Dorghoud, 26, a Marine reservist, came to the ceremony to see his friend, another Marine, become a citizen.

Originally from Egypt, Dorghoud came to Virginia when his father got a job there. He enlisted in the Marines two weeks after graduating from T.C. Williams High School in Alexandria.

He served in the infantry in Iraq in 2006 and in Afghanistan in 2009.

During his tour in Iraq, he was on patrol one day when a call came over the radio that his application for citizenship had been approved. He was invited to a ceremony at Balad air base.

“Coming from the front lines to an Air Force base, it was a like a mini-vacation,” he said.

Now he is studying criminal justice at St. Joseph’s College of Maine and plans to become a police officer. While he was deployed, he said, he never spent much time thinking about who was an American citizen and who wasn’t.

“When you are a Marine, you think about protecting the Marine to your left,” he said.