As the question pertains to the entirety of the United States of America, the answer to the question -- what state is the farthest south in the USA -- is Hawaii. Located in the middle of the Pacific Ocean, at coordinates 21º 18' N, 157º 51' W, the newest of the United States (1959), it is easily the southern-most of the states. Had the question been specific to the continental United States, or the contiguous 48 states, the answer would have been Florida. The island of Key West is the southern-most of the contiguous 48 states, at 24.5592° N, 81.7840° W. Returning to the geographic coordinates of Hawaii, the southern-most tip of the Big Island actually dips down below the 19th parallel. The "official" coordinates for the State of Hawaii (the 21, 18 figure) refers to the position of Honolulu, the state capital that is situated on the island of Oahu.