Contra Dancing is done by all ages, all over the USA, and in fact, all over the world, though it is considered American folk dancing. It bears some resemblance to Square Dancing, but has some significant differences.
All the dances are done to live music. You don’t have to know anything, all you need to know is taught before each dance. You don’t have to have a partner, you are encouraged to dance with different people.
This video is rather long, but it shows how a dance is taught and called.