Complex sentence: He built the first Fort Lisa (also called Fort Manuel) near what is now Bismarck, North Dakota, near a "Gros Ventres" village between the mouth of the Little Missouri and the Knife rivers.
Split into simpler sentences: He built the first Fort Lisa (also called Fort Manuel) near what is now Bismarck, North Dakota. It was a "Gros Ventres" village between the mouth of the Little Missouri and the Knife rivers.