Why are race tracks called Downs?

I was watching a movie last week where there was a Downs I now can’t remember. I think it was in California somewhere and it struck my ear oddly.

Dover Downs is nearby. Churchill Downs hosts the Kentucky Derby every year. But this was a new Downs to me and it got me thinking. I understand where Park and Course come from, but downs?

Why are horse race tracks called downs?

From Who came up with downs? – Harness Racing Newsroom – USTA – USTROTTING

The British and the Irish.

The term downs comes from Great Britain and Ireland where around the year 1500, horse races were held on grassy plains before formal race tracks were built. These grassy areas were known as downs. Later, after real tracks were constructed (usually on the same sites) they named the track and kept the downs in the name. Probably the most famous track there was Epsom Downs which originated around 1661 and became famous for the big race they started known as “The Derby.”