The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States.

Florida Keys and U.S. Route 1, The Overseas Highway

(Update)  I should have added that my son and I have driven from Miami, FL to Key West a couple of times.  The drive on U.S. Route 1 is 165 miles and takes about four hours at a leisurely pace.  Taking your time is worth it to enjoy some of the most spectacular scenery in the United States.