 On 12 October 1861 , the CSS Manassas became the first ironclad to enter combat , when she fought Union warships on the Mississippi during the Battle of the Head of Passes . She had been converted from a commercial vessel in New Orleans for river and coastal fighting . In February 1862 , the larger CSS Virginia joined the Confederate Navy , having been rebuilt at Norfolk . Constructed on the hull of USS Merrimack , Virginia originally was a conventional warship made of wood , but she was converted into an iron @-@ covered casemate ironclad gunship , when she entered the Confederate navy . By this time , the Union had completed seven ironclad gunboats of the City class , and was about to complete the USS Monitor , an innovative design proposed by the Swedish inventor John Ericsson . The Union was also building a large armored frigate , the USS New Ironsides , and the smaller USS Galena . 
 On 12 October 1861 , the CSS Manassas became the first ironclad to enter combat , when she fought Union warships on the Mississippi during the Battle of the Head of Passes . She <a href='been_done' title='1'><mark>had</mark></a> been converted from a commercial vessel in New Orleans for river and coastal fighting . In February 1862 , the larger CSS Virginia joined the Confederate Navy , <a href='been_done' title='2'><mark>having</mark></a> been rebuilt at Norfolk . Constructed on the hull of USS Merrimack , Virginia originally was a conventional warship made of wood , but she was converted into an iron @-@ covered casemate ironclad gunship , when she entered the Confederate navy . By this time , the Union <a href='been_done' title='3'><mark>had</mark></a> completed seven ironclad gunboats of the City class , and was about to complete the USS Monitor , an innovative design proposed by the Swedish inventor John Ericsson . The Union was also building a large armored frigate , the USS New Ironsides , and the smaller USS Galena . 
On 12 October 1861 , the CSS Manassas became the first ironclad to enter combat , when she fought Union warships on the Mississippi during the Battle of the Head of Passes . She done been converted from a commercial vessel in New Orleans for river and coastal fighting . In February 1862 , da larger CSS Virginia joined tdaConfederate Navy , done been rebuilt at Norfolk . Constructed on the hull of USS Merrimack , Virginia originally was a conventional warship made of wood , but she was converted into an iron @-@ covered casemate ironclad gunship , when she entered the Confederate navy . By dis time , thdanion done completed seven ironclad gunboats of thedaty class , and was finna complete the USS Monitor , an innovative design proposed by the Swedish inventor John Ericsson . The daon was also building a large armored frigate , the USS New Ironsides , and the sdaler USS Galena .