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 Fort Henry on the Tennessee River. This was over a month before the combat actions of the ironclads "CSS Virginia" and "USS Monitor" during the March 8–9, 1862 Battle of Hampton Roads.