USS Phlox (1864) was a steamer commissioned by the Union Navy during the American Civil War. She served the Union Navy's struggle against the Confederate States of America as a gunboat; and after the war's end she served the midshipmen at the United States Naval Academy in Annapolis Maryland as a training ship. Given a list of categories: company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, what category does the paragraph belong to?
Mean Of Transportation