THE SMITHSONIAN’S National Museum of African American History and Culture opens on Sept. 24 in Washington after a long journey. Thirteen years since Congress and President George W. Bush authorized its construction, the 400,000-square-foot building stands on a five-acre site on the National Mall, close to the Washington Monument. President Obama will speak at its opening dedication.

Appropriately for a public museum at the heart of Washington’s cultural landscape, the museum’s creators did not want to build a space for a black audience alone, but for all Americans. In the spirit of Langston Hughes’s poem “I, Too,” their message is a powerful declaration: The African-American story is an American story, as central to the country’s narrative as any other, and understanding black history and culture is essential to understanding American history and culture.