Clay County, Florida

Clay County is located in the northeastern part of the U.S. state of Florida along the west bank of the St. Johns River. As of 2020, the population was 218,245 and in 2023, that number increased to 232,439, making it the third largest county in the Jacksonville metropolitan area. While most of the county is unincorporated, there are 4 municipalities with Green Cove Springs being the county seat and the unincorporated Lakeside CDP being the largest place. It is named in honor of Henry Clay, a famous American statesman, member of the United States Senate from Kentucky, and United States Secretary of State in the 19th century.

Since 1990, Clay County has transformed into a largely suburban county with the third highest household median income in Florida behind neighboring St. Johns County and Santa Rosa County. This transformation has come as workers from Jacksonville, and to a smaller extent other nearby cities such as St. Augustine and Gainesville, have moved into newly built residential subdivisions. Over half of workers living in Clay County work in another county, which is the highest rate of any county in Florida. As such, the county has the third highest average commute time in the state at almost 33 minutes. With the population expected to surpass 300,000 residents by 2040, projects such as the First Coast Expressway are being constructed to alleviate chronic congestion on major roadways in the county such as Blanding Blvd and U.S. 17.

Clay County is known for its rich military history with major current and former installations such as Branan Air Field, Naval Air Station Green Cove Springs, and Camp Blanding all being located in the county. The county also attracts many tourists due to its abundance of natural water features. Many notable lakes such as Kingsley Lake, Lake Asbury, Doctors Lake, Lake Geneva, and Lake Brooklyn are all located in the county. Black Creek begins at the St. Johns River just north of Green Cove Springs and runs through the central portion of the county.

The surrounding region was part of St. Johns culture, an early archaeological culture that spanned from 500 BC until the 17th Century, with the arrival of European explorers. At the time of first contact by French Huguenot explorer René Goulaine de Laudonnière, the region was inhabited by the Agua Dulce people under the Timucua chiefdom of Utina. With the arrival of the Spanish colonists to St. Augustine in the East, the wars and skirmishes with the rival tribes to the north and west, and the defeat of the Huguenots at Fort Caroline by the newly arrived Spanish, the Utina chiefdom collapsed and the surviving natives fled South, leaving the area virtually uninhabited until the late 18th Century with attempts to resettle the area by the Spanish in the newly reclaimed Spanish East Florida.

In 1803, Zephaniah Kingsley, purchased the site of Laurel Grove (later rebuilt into the Town of Orange Park) to establish a plantation for planting oranges, and coffee, and for trading slaves. In 1816, George J. F. Clarke purchased land to build a sawmill on the site that grew into the city of Green Cove Springs. During the Patriot War, Laurel Grove was seized by the insurgents, forcing Kingsley to flee, but not before razing the plantation in order to keep it out of rebel hands.

After the war ended and the eventual annexation of Spanish East Florida to the United States, the area saw an influx of tourists and settlers.

Clay County was created on December 31, 1858, from a section of Duval County. The area was once a popular destination for tourists because of its springs and mild climate. Steamboats brought them to various hotels in Green Cove Springs, such as the St. Elmo, Clarendon, and Oakland. President Grover Cleveland was the most prominent of such tourists and had spring water shipped to the White House. Clay County's popularity among tourists peaked during the last three decades of the 19th century. Tourism later waned because of Henry Flagler's extension of the Florida East Coast Railway to other destinations such as Palm Beach and Miami.

The military has also played an important role in Clay County history. In 1939, Camp Blanding opened on Kingsley Lake in southwest Clay County. The Florida National Guard developed this 28,000-acre (110 km²) complex. During World War II, it trained over 90,000 troops and became the fourth-largest "city" in the state. In Green Cove Springs, Lee Field was a flight training center. After World War II, Lee Field became a base for the mothball fleet. Although Lee Field closed in the early 1960s, Camp Blanding continues to operate today as a base for military training. Clay County is also a popular choice of residence for military personnel stationed on bases in nearby Duval County (NAS Jacksonville, NS Mayport, and, before it closed, NAS Cecil Field).