The West Washington Park Neighborhood Association's newsletter this time around bravely mentioned the summer of 1932 race riot in Washington Park. There will eventually be a link at the Association's site here. It was a matter of public record and published history, but not widely known (also little known is the fact that the neighborhood was briefly separately incorporated and did so largely to use zoning laws to shut down saloons on South Broadway). But, neighborhod associations often want to only focus on the bright side of the past.
The newsletter story (based on a book length history of Denver) notes that Japanese Americans were banned from the beach at Smith Lake in 1913, and that African Americans just weren't welcome.
Whites (allegedly communists, and judging by their names, some Hispanic) and blacks from North Denver staged a swim in during the summer of 1932. White beach users violently attacked them, and a park director by the name of Lowry was active in asking them to leave. I suspect that this is the same Lowry after whom the Denver neighborhood is named. This resulted in 17 arrests (7 whites, 10 blacks) with no sign of violence on the part of the protesters.
They were about 25 years too early to catch the wave of the Civil Rights movement, but deserve our gratitude none the less. Today, particularly on holidays like the 4th of July, Washington Park reflects Denver's diversity, although the beach is gone, replaced later by an indoor swimming pool.