Olivia Cousins can trace her family in the United States to a soldier who joined the rebelling colonists when he was just 17. But when a friend suggested she join the Daughters of the American Revolution, an organization whose members can prove they are related to someone who aided the rebels in 1776, Dr. Cousins nearly laughed.


Dr. Cousins is black. And the D.A.R., as it is commonly called, is a historically white organization with a record of excluding blacks so ugly that Eleanor Roosevelt renounced her membership in protest.


Yet last week, in a circa-1857 stone chapel in Jamaica, Queens, Dr. Cousins was named an officer in a small ceremony establishing a new chapter. Her daughter took photos. The pictures documented a singular moment for the D.A.R., founded in 1890: 5 of the 13 members of the new chapter are black.


Perhaps more strikingly, the Queens chapter is one of the first in the organization’s nearly 122-year history that was started by a black woman: Wilhelmena Rhodes Kelly, from Rosedale, who is also its regent, or president. Ms. Kelly traces her origins to the relationship between a slaveholder and a slave, who appear to have considered themselves married, and her new position is part of a remarkable journey for both her family and the organization.


“My parents understood that they were Americans and that they were a real important part of the American story,” said Dr. Cousins, who, like the other members, is a passionate student of genealogy. Her Revolutionary War ancestor was a free man of mixed race. “Their whole thing was that segregation is unacceptable,” she said of her parents. For her, she said, “de facto segregation was unacceptable.”


Racism and the vicissitudes of history have long kept the number of minorities in the D.A.R. low. Only about 5,000 of the nearly 400,000 American soldiers in the Revolution were black, said Eric Grundset, director of the organization’s library. Some were freed slaves who joined voluntarily, others slaves who bartered their service against promises of earning their freedom (which were often reneged on), and others sent to fight in place of the men who owned them.


“To the best of my knowledge, we have never had both an African-American charter regent as well as this percentage of members,” said Denise Doring VanBuren, the organization’s New York regent, who presides over the 7,000 members in the state.


Dr. Cousins, a professor of medical sociology at Borough of Manhattan Community College, joined the group with two of her sisters, who are both substitute teachers: Collette Cousins, who lives in Durham, N.C., and Michelle Wherry, who lives in Lewis Center, Ohio. They will commute to the monthly meetings in Queens.


Ms. VanBuren said the D.A.R. tried in recent decades to attract members of diverse backgrounds.


In doing so, it had to overcome as many decades of bad press.


“Because of their reputation, they are probably not going to attract very many African-Americans,” said Raymond Arsenault, a professor of Southern history at the University of South Florida, St. Petersburg, and a civil-rights historian. “So this is quite striking that this is happening.”


Dr. Arsenault is the author of “The Sound of Freedom: Marian Anderson, the Lincoln Memorial and the Concert That Awakened America,” a book that chronicles the episode that stamped the D.A.R. at the time as racist. In 1939, the group barred Anderson, a world-famous black contralto, from performing in its Constitution Hall in Washington, prompting Eleanor Roosevelt, then the first lady, to renounce her membership, and fomenting a national conversation about race.


“In the context of the Marian Anderson story and its complicated legacy, it seems like something of a milestone,” Dr. Arsenault said of the Queens chapter.


Dr. Cousins said, “When most African-Americans hear about the D.A.R., we go straight to Marian Anderson, and we get stuck there.”


Nevertheless, joining was “a no-brainer,” she said. “I’m a part of this country, and my presence needs to be recognized.”