There's a bridge with over 6,000 locks on it near my grandparents' house. It is *right* over the Ohio River (which is owned by West Virginia, wtf), and people get married/propose there. It is apparently a tradition to put a lock on one of the steel cables, and write the year on it. Then you throw the key into the river.
They passed a law just to stop people from doing it. Also, there's at least 6 locks dated "3017" because they are living in the wrong millennium.