The museum, which opened in September 2016, typically requires visitors to reserve timed-entry passes two months in advance. The advance timed passes are released on the first Wednesday of every month—and they go quickly. All of the timed passes for July (which were released April 4) are gone. The next release of timed passes will be May 2 for the month of August. Even with the passes, the museum has struggled at times with overcrowding.

But in April, the museum will let visitors enter the museum on a first-come, first served basis.

The effort by the Smithsonian, called Walk-Up Wednesdays, aims to test the no-pass entry. The Walk-Up Wednesdays will be April 4, April 11, April 18, and April 25. People who already have advance timed passes will receive priority, according to the museum.

The African American History Museum offers a limited number of online passes every day beginning at 6:30 a.m. A limited number of walk-up passes are also available starting at 1 p.m. weekdays. But until this experiment, there was no way for a person to walk up without a pass and stand in line. During the month of April, the museum will not issue walk-up or online passes on Wednesdays.

Entry into the National Museum of African American History is free like the rest of the Smithsonian museums in D.C. The museum has a wide ranging collection of African American history from the Civil War era and the American South to topics such as fashion, music, segregation, literature, military, and religious groups. There are 36,000 artifacts in the museum, including items from the sunken slave ship São José Paquete Africa, Harriet Tubman’s hymnal, a segregated drinking fountain from the Jim Crow era, Muhammad Ali’s boxing gloves, and former president Barack Obama’s 2008 presidential campaign materials.