Converted at Cairo, Illinois, into an ironclad ram for use by the Union Army, she sailed from that port late in August under the command of Captain Phelps for duty in the Mississippi River between Island No. 10 and the mouth of the White River, Arkansas. She was back at Cairo, Illinois, for repairs when, on 1 October 1862, "Eastport" and the other vessels of the Western Flotilla were turned over to the Navy and joined the Mississippi Squadron.