From the USPS, September 20, 2016:
[Technically, “Celebrating African American History and Culture,”] this stamp celebrates the National Museum of African American History and Culture. Occupying a 5-acre site on the National Mall in Washington, DC. The museum is the 19th Smithsonian museum and the only national museum devoted exclusively to African-American life, art, history and culture. The stamp is based on a photograph of the museum by Alan Karchmer showing a view of the northwest corner of the building. Text in the upper left corner reads “National Museum of African American History and Culture.” Art director Antonio Alcalá designed the stamp.