When Maria Valles Vda De Bonilla moved to the United States from El Salvador 16 years ago – aged 90 – there was one thing she requested: to become a citizen.

She wanted to be able to vote in the adopted country she loves, something she was never able to do in El Salvador – first because it was not legal for women to vote, and later because the polling locations were too far away and the journey was unsafe.

On Tuesday afternoon, at age 106, Ms Bonilla sat in her wheelchair in a bright sapphire dress in the US Citizenship and Immigration Services office in Fairfax County, Virginia, and took her oath of citizenship. She waved a tiny American flag and smiled, her eyes moist with tears.

"I am so happy, there are no words," said Ms Bonilla, who was surrounded by 18 family members who came to celebrate.

Ms Bonilla – who lives in Gainesville, Florida, with her daughter, grandchildren and great-grandchildren – is not registered to vote in Virginia, so she did not get to cast a ballot vote in the midterm elections after her ceremony. But when you become a citizen at age 106, you are an optimist.

"Next time," she said, speaking in Spanish. "God willing."

It was a coincidence that the ceremony fell on an election day, she was part of a routine naturalisation ceremony with 12 other people from various countries, including Italy, India, Mexico, Cameroon and Thailand.

She is not the oldest person to be naturalised in the US. That honour goes to a Turkish immigrant who at age 117 took the oath in Los Angeles almost 20 years ago.

But Ms Bonilla is the oldest in recent memory, said Kimberly Zanotti, director of the Washington Field Office, who has worked at the office for seven years and in the Newark office for 18 years before that.

"It's fantastic," Ms Zanotti said.

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Ms Bonilla was born on 22 March 1912 and lived in rural El Salvador, farming beans, corn, rice and lettuce for most of her life. She had 18 children, according to her youngest daughter Bernarda Bonilla, 55. But only eight are still alive. Her husband died many years ago, nobody remembers exactly when, her daughter said. Her oldest child is now 75.

Women got the right to vote in El Salvador in 1939 when Ms Bonilla was 27 years old. But she lived far from a polling location for many years and never made the trip. When she got older, she moved to San Salvador, where the streets were too dangerous for her to leave the house and vote, according to her granddaughter Diana Cortez.

"You can't just walk around, no way," said her granddaughter Diana Cortez, 36. The criminal gang "MS-13 has taken over the country".

Freedom is one of the things that delights Ms Bonilla about this country, Ms Cortez said.

"She can walk around, go outside day or night, without any fear," said Ms Cortez, who is a manager at a health clinic. "We can't do that in El Salvador because of the crime."

Ms Bonilla came to the United States in 2002 to follow her children, who were all living here, and were worried about her living on her own at age 90. She also wanted to spend time with her grandchildren, who were all born here.

When she arrived, she immediately fell in love with her new home. But in recent years, her heart has started to give out, Ms Cortez said. In April, she had two heart attacks on the same day and almost died.

"She asked God to give her extra time to so this could happen," Ms Cortez said about her citizenship.

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When they got home from the hospital, Ms Cortez filled out her grandmother's citizenship application and asked for a medical waiver, meaning Ms Bonilla would not have to complete the civics and language exam in order to become naturalised. The waiver was granted last week after she was interviewed by immigration officials who reviewed her paperwork. Because of her health and age, immigration officials decided to have her ceremony quickly.

Ms Bonilla was one of 19,000 people naturalised in the Washington Field Office in the past year and one of about 750,000 naturalised each year across the country.

Ms Cortez said her grandmother was honoured to be part of that group. She said the secret to her grandmother's longevity was a will to live.

"She never thought she'd live that long, to be honest," Ms Cortez said. "She doesn't know why God decided to have her here at almost 107. He must have a reason for her to be here. She wants to be here."

Then Ms Cortez paused and added another small clue.

"But grandma does like her tequila," she said. "We give her a shot sometimes. The doctor says not too much. He also says that she's 106, she can do what she wants."