Marcus Mills and Alice Bonner are training as docents for the National Museum of African American History and Culture. Bonner said the institution, which opens Sept. 24, will become a “house of healing” for the country. (Dayna Smith/For The Washington Post)

For Alice Bonner, the National Museum of African American History and Culture is even more important than the election of Barack Obama as the nation’s first African American president. Obama’s election was historic, she said, but the museum will be here forever, serving as a sacred place, a balm for the wounds of African Americans and a “house of healing” for the entire country.

“I have been waiting for this museum all my life,” Bonner, 67, said. “It is the most needed institution in Washington in a very long time.”

The Silver Spring resident and retired media executive has been volunteering at the museum for seven years. She gives tours in the temporary galleries at the Smithsonian Institution’s National Museum of American History, has helped curators search eBay for artifacts and staffed the visitor center at the construction site on Constitution Avenue and 14th Street, next to the Washington Monument.

Her passion is deep and personal. “We were miseducated about African American history, mostly by omission, by distortion,” Bonner said.

When the museum opens Sept. 24, Bonner will be part of the effort to change that.

Bonner is one of about 300 volunteers preparing for the museum’s opening in four months. Selected from a thousand applicants, they will be on the front lines, assisting visitors and helping to improve their experiences. Given the large applicant pool, museum officials were choosy when “hiring” the unpaid workers. They accepted women and men, African Americans and whites, the disabled and the able-bodied into the training programs. Retirees, federal workers, a former ambassador, history teachers, students, law enforcement officials and volunteers from other Smithsonian museums are part of the corps.

“We looked for people of all ilks,” Director of Education Esther Washington said. “We want our museum to look like the rest of the world.”

The volunteers signed up for different reasons. Some like Bonner, who integrated her rural Virginia high school in the 1960s, lived the history that will be told.

“It has to do with validation,” Bonner said about her motivation to volunteer. “I’ve spent most of life, from age 16 forward, being a part of inclusive institutions . . . but most of what I have experienced in those many institutions, to a greater or lesser degree, reminded me that I come from a secondary group of people.”

Others are museum lovers: Angel Thompson, 25, of Washington hopes her experience will prepare her for a future museum career. Susan Schmidt, 62, of Bethesda is looking ahead to retirement and an activity that is intellectually enriching and fun.

Many want to be part of what they call a game-changing institution. The museum “doesn’t just influence you in the museum space, but socially and culturally,” said D.C. resident Jennie Chaplin, 51, a former congressional staffer and teacher. “It’s a space for everybody.”

The sheer number of people wanting to help has astounded Washington, a 26-year veteran of the Smithsonian. She has never witnessed this level of enthusiasm.

“We didn’t even have to recruit, and they are still pouring in,” Washington said, adding that they are not accepting applications currently. “It’s an embarrassment of riches.”

The city, which is renowned for its museums, has a long tradition of volunteering. The Washington metropolitan area ranks eighth in the country, with 32 percent of residents volunteering their time in 2014, according to the Corporation for National and Community Service, a federal agency. In all, volunteers provided 197.4 million hours of service in 2014, the most recent year available.

Applicants must commit to two years of helping at least four hours each month. They must complete training programs that include online reading assignments and quizzes and in-person lectures and role-playing exercises.

“This is hard. I told them, ‘We’re going to kill you with this training,’ ” Washington said, adding that she doesn’t intend to scare them. “I tell them I have never lost a volunteer. I’ve never left anybody behind. You’re going to be okay.”

The largest group, numbering 230, are spending four months being trained as visitor information advocates who will staff the information desk in the museum’s central hall and circulate throughout the building. Their primary responsibilities are to welcome guests, give directions, manage lines, distribute interactive devices and help visitors with special needs. They also will be trained to offer empathy and tissues when needed.

Fatigue will be their biggest challenge, Washington said. “We’re warning them, ‘You’re going to answer the same question many times a day, and you always answer as if it’s the first time.’ ”

Thompson knows the drill after many hours of staffing the museum’s visitor center during construction. “I knew I wanted to work in a museum, I just didn’t know what I wanted to do,” said Thompson, a master’s degree student in museum studies at Morgan State University in Baltimore. “I like interacting with people.”

Schmidt is preparing for retirement. Her parents “raised me to be a volunteer,” she said, and she looked for a position that would involve art and museums, two of her passions.

“It’s the most challenging experience since graduate school,” Schmidt said of the training.

Another 54 volunteers have signed up to be docents who will lead tours of the galleries. This group, which includes many who have been giving tours of the museum’s temporary gallery at the National Museum of American History, are halfway through their rigorous nine-month training, known as Docent University.

“It’s like a master’s degree in history,” said Marcus Mills, 42, of Washington.

Mills signed up in 2009 when he was unemployed. Now a senior financial systems analyst for a government contractor, he continues to give one Saturday a month. He often shares his four-hour shift with Bonner, much to his delight. “She’s forgotten more about African American history than I know,” he said.

The museum hired a university professor to teach the history material, based on John Hope Franklin’s seminal book, “From Slavery to Freedom.” In addition to the lectures and online assignments, the docents will be observed giving trial tours by the museum’s education staff members.

“They want to make sure you’re personable . . . and know what you’re talking about,” Mills said.

Chaplin said she has no butterflies. “We have been training and we’re surrounded by top-notch scholars, top-notch educators,” she said. “We’ve been groomed. We’re ready.”