Original sentence: (This conflict is also known as the American Civil War, although War Between the States is the only name ever formally used by the United States Congress.For further information see the American Civil War page on naming conventions.He is most famous for serving as the only President of the Confederate States of America throughout the War Between the States
Edited sentence: He is most famous for serving as the only President of the Confederate States of America throughout the American Civil War (also known as the War Between the States)