Philanthropist and media mogul Oprah Winfrey is donating $12 million to the Smithsonian’s National Museum of African American History and Culture, officials announced Tuesday. Combined with the $1 million she gave in 2007, it is the museum’s largest donation, and Winfrey’s name will go on a 350-seat theater in recognition. The chairwoman and chief executive of the Oprah Winfrey Network has been a member of the museum’s advisory council since 2004.

“I am so proud of African American history and its contributions to our nation as a whole,” Winfrey said in a statement. “I am deeply appreciative of those who paved the path for me and all who follow in their footsteps. By investing in this museum, I want to help ensure that we both honor and preserve our culture and history, so that the stories of who we are will live on for generations to come.”

The museum’s founding director, Lonnie G. Bunch, says: “Every donation, whether $25 or a $10 million corporate donation, is important. But truly, there’s only one Oprah Winfrey.”

Winfrey has been with the museum as an adviser and supporter for nearly a decade, Bunch says. “In essence, she’s put her imprimatur on it. Part of getting a museum built is tied to visibility helping all people see how important it is. Oprah Winfrey is someone so many people in America admire, and I think this is an important moment to the museum.”

Ground was broken on the five-acre site, adjacent to the Washington Monument, in February 2012. Congressional funding accounts for half of the museum’s $500 million design, construction and exhibition costs. The museum is raising the remaining $250 million.

The museum has received a $10 million donation from both the Gates Foundation and the Lilly Endowment, Bunch says, and “we have raised over $335 million in federal and private” funds. Of that amount, “over $140 million has been raised from individuals, corporations and nongovernmental sources,” with Winfrey’s gift being a milestone.  

“For a woman like her to give the museum that kind of gift now, before it is open, is really a vote of confidence and encouragement,” said Maria Di Mento, a staff writer for the Chronicle of Philanthropy.

The Winfrey donation is in a league with other large donations, which are plentiful in Washington. The announcement comes after Monday’s news that a $13.5 million gift to the Foundation for the National Archives, from philanthropist and co-founder of the Carlyle Group, David M. Rubenstein, will fund a new gallery and plaza there. Rubenstein also gave $50 million to the Kennedy Center for renovations in January and $10 million for a George Washington library at Mount Vernon in February.

Recent large Smithsonian gifts include $10 million last October from Michael Tennenbaum, senior managing partner of Los Angeles-based Tennenbaum Capital Partners, and his wife, Suzanne, to study coastal marine biodiversity, and $35 million to the National Museum of Natural History in May 2012 by David H. Koch, the executive vice president of Koch Industries. Last June, Roger Sant, a well-known Washington philanthropist, and his wife, Victoria, gave $10 million to the National Museum of Natural History to endow its director’s post.

There are a lot of wealthy people here, and there are those “who don’t live in Washington but do a lot of business and lobbying here,” Di Mento said. They know the city and are familiar with Washington institutions. “It’s the nation’s capital, and doing anything here is going to make a splash.”

The Museum of African American History and Culture, which hosts a gallery at the National Museum of American History, is scheduled to open in 2015.