The Spanish explorer Juan Ponce de León (Ponce de León, Juan), in search of the legendary Fountain of Youth, landed there in 1513 and took possession of the territory for Spain. In 1564 France established Fort Caroline near the mouth of the St. Johns River (Saint Johns River), about 35 miles (55 km) north. A year later, in order to maintain Spanish sovereignty over Florida, Pedro Menéndez de Avilés (Menéndez de Avilés, Pedro) destroyed the French colony and founded the city, which he named for St. Augustine (Augustine, Saint), bishop of Hippo, upon whose feast day he had sighted the coast. Except for the 20 years (1763–83) that Florida belonged to England, throughout the following 256 years it was the main northern outpost of the Spanish colonial empire.

St. Augustine's economy is based on tourism (first promoted in the 1880s by the financier-railroad magnate Henry M. Flagler (Flagler, Henry M), a pioneer in Florida development), services, industry (including aircraft modification and the manufacture of aluminum products and boats), and commercial and sport fishing. The parent company of the Florida East Coast Railway has its headquarters there. Many Spanish colonial buildings and sites have been restored, including the cathedral (1791), Oldest House (begun in 1723), Ximenez-Fatio House (c. 1797), and the Spanish Quarter, a restored 18th-century village. The city has several museums, including the Lightner Museum, the St. Augustine Lighthouse and Museum, and the Government House Museum. Marineland of Florida is about 15 miles (25 km) south. Southeast of the city on Anastasia Island are Anastasia State Recreation Area and Fort Matanzas National Monument. The city is the seat of Flagler College (1968), whose main building is the first large hotel built (1888) by Flagler. Pop. (2000) 11,592; (2007 est.) 12,284.