President Barack Obama and first lady Michelle Obama joined four generations of the Bonner family, including a then- 99 year-old Ruth Odom Bonner, at the opening of the National Museum of African American History and Culture last fall. (Jonathan Newton/The Washington Post)

Ruth Odom Bonner was 99 when she grasped the rope of the old Baptist church bell and started it tolling across the Mall last fall before a gathering of thousands.

It was a sublime moment. “Mother Bonner,” as the staff at her assisted-living community called her, was the daughter of a man born into slavery and had lived through almost a century of racial oppression and segregation.

Now here she was, ringing the hallowed bell to officially open the Smithsonian Institution’s National Museum of African American History and Culture in Washington.

The graying man who stood behind her steadying her arm was the country’s first black president, Barack Obama.

Bonner, who cherished that day, died peacefully in her sleep Friday in the Silver Spring assisted-living facility, her son, Michael, said Wednesday. She had turned 100 on March 16.

She and the four generations of her family reflected “the arc of our progress,” Obama told them that Saturday as they assembled on the stage for the grand opening of the museum.

“And the sound of this bell will be echoed by others . . . all across this country — an echo of the ringing bells that signaled emancipation more than a century and a half ago,” he said. “The sound, and the anthem, of American freedom.”

The 500-pound bell had been lent by the First Baptist Church in Williamsburg, Va., which was founded by slaves and free blacks in 1776. The bell was acquired in Cincinnati in 1886.

Bonner, clad in a magenta pantsuit, stood and got a kiss on the cheek from the president. Then both, along with first lady Michelle Obama and Bonner’s great-granddaughter, Christine, 7, hauled on the rope and got the bell ringing.

Bonner “was beaming all day,” her granddaughter, Rukiya Bonner, said Wednesday. “She was the belle of the ball.”

“She was proud to be part of history,” Bonner said. “She was thankful that such an institution existed . . . She felt honored to meet Obama, because she would never think that in her lifetime she would see such a wonderful president who happened to be black.”

“The whole family was talking about it all day long,” she said of the museum’s opening Sept. 25. “That extended into Christmas . . . It was a surreal moment . . . a wonderful way to sum up a lot of her life experiences.”

A former political precinct leader in Cleveland, where she spent much of her life, Ruth Bonner was determined to walk up the steps of her polling place in Northeast Washington and cast her vote for Obama when he was first elected in 2008, her son said.

But meeting the president was not her only thrill last year.

She and her family were taken to the museum well before the ceremony began, her son said.

“We were among the first at the museum” in the celebrity waiting room, he said.

So “she was able to interact with all of the dignitaries and stars that came through the . . . room,” he said. “It was just unimaginable. President Clinton to Oprah to Will Smith . . . She really was elated with that.”

And the stars were eager to meet her, he said.

Bonner was born in 1917 in tiny Biscoe, Ark., one of the eight children of Elijah and Ada Odom. Her father had been born into slavery in 1859 but had gone on to become a physician after the Civil War.

He had a practice in Biscoe that he ran out of the back of his general store.

There were few doctors in the area, and the local white residents would allow him to care for them but not deliver white babies, Michael Bonner said.

In the 1930s, Ruth Odom was sent north to Cleveland to get a better high school education.

There, she met her husband, William H. Bonner Sr., a bus driver. After high school, she worked as a bookkeeper and later as a teaching assistant in the Cleveland school system.

She also took college courses to help her work in the classroom, her son said. William Bonner died in 1990 after over 50 years of marriage, he said. They had two children, Michael and William H. Bonner Jr.

She “will be remembered . . . for her warmth, sacrifice, and love,” the museum’s founding director, Lonnie G. Bunch III, said in a statement Wednesday.

“She will also be remembered for representing generations of African Americans with honor and dignity,” he said. “This nation owes Mrs. Ruth Bonner a debt of gratitude.”

A memorial service is set for Sept. 9, at Washington’s Nineteenth Street Baptist Church. Donations to the museum can be made in lieu of flowers.