Built in the late 1700s for the municipal government, this National Historic Landmark was the site of the Louisiana Purchase transfer in 1803, housed the Louisiana Supreme Court when it issued the landmark Plessy v. Ferguson decision and at one time served as a prison. It now houses a comprehensive exhibit about Louisiana's early history. Open 10 a.m. to 4:30 p.m. Tuesday through Sunday. Closed holidays. Admission $6 adults; $5 seniors, students and active military personnel; free for children 12 and younger.