Grant Prince Marsh (May 11, 1834 – January 1916) was a riverboat pilot and captain who was noted for his many piloting exploits on the upper Missouri River and the Yellowstone River in Montana from 1862 until 1882. He served on more than 22 vessels in his long career. He started his career in 1856 as a cabin boy and continued his career for over 60 years becoming a captain, riverboat pilot and riverboat owner. During his career he amassed an outstanding record and reputation as a river steamboat pilot and captain. His piloting exploits became legendary and modern historians refer to him as "Possibly the greatest steamboat man ever", "possibly the greatest [steamboat pilot] ever", "possibly the finest riverboat pilot who ever lived", "the greatest steamboat master and pilot on both the Miss