The Spanish built Fort Matanzas in 1740-42 to control Matanzas inlet, the "back door" to St. Augustine. Much earlier, in 1565, Spain had bloodily crushed here a French challenge to her control of Florida by killing the remnants of a French colony from Fort Caroline, 40 miles to the north. Fort Matanzas became a National Monument in 1924, preserving this unique specimen of a vanished style of military architecture and engineering.