The new ram joined Rear Admiral David Dixon Porter's Mississippi Squadron above Vicksburg in time for the famous dash on 16 April 1863 past the deadly batteries which protected the vital Confederate fortress. The gunboats engaged the southern guns as they shepherded Army transports through the gauntlet to New Carthage. Ram "General Sterling Price" was lashed to the starboard side of "Lafayette" for the passage. The ships were covered with heavy logs and bales of wet hay, which proved to be an excellent defense. Each ship, except , also towed a coal barge. "Lafayette", hampered by the ship lashed to her side, received nine "effective" shots through her casemate and had her coal barge sunk. Although under fire for 2½ hours, all ships of the squadron were ready for service within half an hour after the passage. The successful steaming of the squadron past the heavy batteries contributed to the early seizure of Grand Gulf, the eventual fall of Vicksburg itself, and ultimately the conquest of the entire Mississippi River.