Basically, this is where jazz was invented, or at least where it originated from. On Sundays, enslaved Africans were allowed to assemble here to do their thing. They danced, sang, made music, traded, hung out. And you know, when oppressed peoples get together, things start to happen. Eventually there was jazz, which led to R&B, and rock, and hip hop - basically all American music.
Park hours are 8am to 6pm.