MHA Nation The Mandan, Hidatsa and Arikara Nation, also known as the Three Affiliated Tribes, is located on the Fort Berthold Indian Reservation in central North Dakota. The reservation is located on the Missouri River. The Tribal Council headquarters is located 4 miles west of New Town, ND. The MHA Nation Tribal Business Council invite you to visit the Fort Berthold Reservation and learn more about our government, culture and history.