The foundation plans to announce the gift Saturday during an event at National Harbor. The foundation chose the museum to receive its 2013 Legacy Grant to be used for ongoing construction of the museum.
The museum is under construction near the Washington Monument. It's scheduled to be completed in late 2015 or early 2016.
Congress pledged to provide half the $500 million cost. The Smithsonian has been working to raise the remaining funds from private sources. Oprah Winfrey is among the largest donors, giving $13 million.
The Links Foundation is the philanthropic arm of The Links, an organization of professional women of color.