Captain of a gun on board the USS Varuna during the attacks on Forts Jackson and St. Philip and in action against the rebel ship Morgan, 24 April 1862. During this action at extremely close range, while his ship was under furious fire and was twice rammed by the rebel ship Morgan, McKnight remained steadfast at his gun throughout the thickest of the fight and was instrumental in inflicting damage on the enemy until the Varuna, so badly damaged that she was forced to beach, was finally sunk.