 Complete the following phrase:  The last were so hardy that the Navy sent them into service in the Gulf of Mexico, where they supported the successful Federal attack on the Confederate port city of Mobile. All senior officers in the Western Theater, including Grant and Sherman, agreed that Eads and his vessels had been vital to early victory in the West. The first four gunboats were built at the Eads Union Marine Works in Carondelet, Missouri. The next three were built under Eads contract at the Mound City Illinois Marine Railway and Shipyard. Eads vessels were the first United States ironclads to enter combat. On January 11, 1862 the Eads-built ironclads St. Louis and Essex fought the Confederate gunboats CSS General Polk, CSS Ivy, and CSS Jackson at Lucas Bend, on the Mississippi River. Subsequently, on February 6, 1862, Eads ironclads captured 