Grant Marsh is most often referenced by historians for his exploit in 1876 as the pilot of the "Far West", a shallow draft steamboat operating on the Yellowstone River and its tributaries, which was accompanying a U.S. Army column that included Lt. Colonel George Armstrong Custer and the 7th Cavalry. The army column was part of the Great Sioux War of 1876, and its most noted battle was the Battle of the Little Bighorn, often known as "Custer's Last Stand" on June 25–26, 1876. After the battle, from June 30 to July 3, 1876 Grant Marsh piloted the "Far West" down the Yellowstone and the Missouri Rivers to Bismarck, carrying fifty-one wounded cavalry troopers from the site of the defeat of Lt. Colonel George Armstrong Custer at the Battle of the Little Bighorn. He brought the first news of the "Custer Massacre" which was disseminated to the nation via telegraph from Bismarck. Most noteworthy in riverboat lore, Grant Marsh set a downriver steamboat record, traversing some 710 river miles in 54 hours.