Fort Walton Beach was home to Native American mound builders centuries before it had its name. In the middle of today's downtown stands the Fort Walton Mound, a ceremonial earthwork 12 feet high and 223 feet wide at its base. It was built by people of the Pensacola culture, a regional form of the Mississippian culture; estimates of its age vary widely, from around 800 CE to as late as the 1500s. The site gave its name to the "Fort Walton culture" of archaeology. It was designated a National Historic Landmark on July 19, 1964, and the Indian Temple Mound Museum, which first opened beside it in 1962, is now part of the city's Heritage Park and Cultural Center.
More about Fort Walton Beach
The town's European-American history began in 1838, when John Anderson and Andrew A. Alvarez received land here, and the place appeared on maps as Anderson until 1884. In 1861 the Confederate army set up Camp Walton, manned by the "Walton Guards," to watch the narrows of Santa Rosa Sound for Union ships; the post was abandoned in August 1862. The name came from Walton County, itself named for Colonel George Walton, secretary of West Florida under Andrew Jackson in 1821 and 1822. On April 11, 1879, John Thomas Brooks bought 111 acres at an auction in Milton, land that became the downtown.
The community stayed small for decades: the post office changed its name from Camp Walton to Fort Walton on March 1, 1932, and the 1940 census counted just 90 residents. Fort Walton was incorporated effective June 16, 1941, and the growth of nearby Eglin Field during and after World War II transformed it. In 1950 Okaloosa County acquired 875 acres of Santa Rosa Island for $4,000, which became Okaloosa Island, and on June 15, 1953, the town became Fort Walton Beach. By 1960 it had 11,249 residents.
Sources
Wikipedia: Fort Walton Beach, Florida (citing Hutchinson, 1961, and the Playground News)
Wikipedia: Fort Walton Mound (citing the National Park Service)