High Quality Content by WIKIPEDIA articles! The Jamestown Dam is a rolled-earth dam spanning the James River in Stutsman County in the U.S. state of North Dakota, serving the primary purpose of flood control. It is located north of the city of Jamestown, North Dakota. Built from April 1952 to September 1953, the dam measures 1,418 feet (432 m) long at the crest and 85 feet (26 m) high. It impounds the James River to form the Jamestown Reservoir. A small islet lies shortly upstream of the dam, where the James River previously split into two channels.