Interestingly, the article then wanders into a discussion of how the pool has never had swimming allowed, but obviously this was not always strictly enforced, as this photo from the 1920's shows:
Where did they swim officially around Washington?:
According to the site Histories of the National Mall, the District of Columbia operated three small whites-only public pools near the Washington Monument in the mid-1920s and early '30s, which were demolished in 1935.Considering that the Brisbane Spring Hill Baths, which I wrote about in detail in 2011, were opened in 1886, it would seem we were pretty advanced compared to other cities in providing that type of facility.
The site says that starting in the 1880s, there were segregated swimming areas near the Mall in the Tidal Basin: "In 1914, Congress voted to create an official beach on the Tidal Basin for white patrons. African Americans swam nearby in a segregated area that never received funding or buildings. Facing increased criticism from black leaders and concerns that the water was polluted, Congress voted to ban swimming in the Tidal Basin in 1925."