Obviously something horse related - but you would think it would be horse racing.
Nope, it's...of all things...jousting. Ring jousting, to be precise. It became the state sport in 1962. (In fact, Maryland is the only state with an official state sport. And it's jousting. Because Maryland is weird).
The rings can be as small as 1/4 of an inch in diameter and you have to get them on your lance at full speed. With only one hand on the reins.
This is actually a Canadian ring jouster because I couldn't find one from Maryland. (The sport is similar to "tent pegging").
Image source: Wikimedia Commons.