Sioux Falls, South Dakota is 41% larger than Fargo, North Dakota.
Area: 120 km2 calculated
Fargo is the largest city in the State of North Dakota, accounting for nearly 16% of the state population. Fargo is also the county seat of Cass County. According to the 2013 United States Census estimates, its population was 113,658. Wikipedia
Area: 170 km2 calculated
Sioux Falls is the largest city in the U.S. state of South Dakota. It is the county seat of Minnehaha County, and also extends into Lincoln County to the south. Wikipedia