Located on U.S. Highway 1, at approximately mile marker 47, at the western end of Key Vaca.

Gerdes, in his "Reconnaissance of the Florida Reefs and all the Keys" (1849) states, "The Id. West of Cow Key (Key Vaca) is named Nights Key, or Knights."

Prior to the completion of the Key West extension of the Florida East Coast Railway, when this was the end of the line, a major seaport existed here. A U.S. Post Office was established here in 1908, and operated until June, 1912. A U.S. Coast & Geodetic Survey field report written in 1935-36 states: "The key was named after the original settler and is called locally Knights Key."