Middleburg is an unincorporated area and census-designated place within Clay County, Florida, United States, located 26 miles southwest of downtown Jacksonville and 16 miles northwest of Green Cove Springs, the Clay County seat. It is home to Middleburg High School.
The communty began in the 19th century with several different names. It was first known as Clark’s Ferry from the 1820s to 1833. From 1833 to 1850 the area was then known as Gary’s Ferry after Samuel Y. Gary. On September 8, 1853 the area was finally called Middleburg. The new town traded in timber, citrus fruits and crops from farmland. When Clay county was created in 1858 Middleburg became the temporary county seat until 1874.
As of the census of 2010, there were 13,008 people living in 4,891 housing units within the CDP.