Part of the Greater Jacksonville Metropolitan area, Clay County is located in northeastern Florida. Clay County contains 601square miles of land area and 43 square miles of water surface. The county seat is Green Cove Springs.

Clay County was carved out of Duval County when it was designated by the Florida Legislature on December 31, 1858. The county was named in honor of Henry Clay, a former Senator from Kentucky who also served as the US Secretary of State for several years in the earlier 1800's.

In the early days, Clay County, with its therapeutic warm springs and temperate climate, was a popular destination for tourists from the northern states. Most folks visiting the area came on steamboats. The local spring water was of such quality that President Grover Cleveland had it shipped to the White House. Then Henry Flagler built the Florida East Coast Railway along the coast and the tourists headed south for places like Palm Beach, Fort Lauderdale and Miami.

During World War II, the American military built and operated several training bases in Clay County, effectively turning Camp Blanding (in the center of Clay County) into the 4th largest city in Florida for a few years. These days, Clay County is a popular residential location for military personnel (and retirees) because of the proximity to still-operating bases in nearby Duval County.