|• Total||19.6 sq mi (50.7 km2)|
|• Land||19.6 sq mi (50.7 km2)|
|• Water||0 sq mi (0 km2)|
|Elevation||33 ft (10 m)|
|• Density||665/sq mi (256.8/km2)|
|Time zone||UTC-5 (Eastern (EST))|
|• Summer (DST)||UTC-4 (EDT)|
|GNIS feature ID||0286819|
Middleburg is an unincorporated area and census-designated place (CDP) within Clay County, Florida, United States, located 26 miles (42 km) southwest of downtown Jacksonville and 16 miles (26 km) northwest of Green Cove Springs, the Clay County seat. It is home to Middleburg High School. As of the 2010 census, the population of Middleburg was 13,008. It is home to the Middleburg Historic District (Florida)
Middleburg is located northwest of the center of Clay County at  Florida State Road Blanding Boulevard leads northeast 13 miles (21 km) to the Orange Park area and southwest 23 miles (37 km) to Keystone Heights.(30.050783, -81.902013).
As of the census of 2010, there were 13,008 people living in 4,891 housing units within the CDP. Between the 2000 and 2010 census, Middleburg realized a population increase of 2,670 individuals. The racial makeup of the CDP was 92.9% White, 3.1% African American, 0.6% Native American, 0.7% Asian, 0.0% Pacific Islander, 0.9% from other races, and 1.8% from two or more races. Hispanic or Latino of any race were 4.1% of the population.
In the CDP, the population was spread out with 24.87% under the age of 18, 75.13% age of 18 or over, and 10.36% age of 65 or over. The population is 49.7% female and 50.3% male.
Middleburg began in the 19th century with several different names. It was first known as Clark's Ferry from the 1820s to 1833. The name derived from Asa Clark who ran the ferry until 1828. In 1828 the Black Creek Methodist Church was founded by Isaac Boring but the frontier Methodist society met in their own homes until the Methodist United Church was built in 1847. Fort Heilman protected settlers at Clark's Ferry where it was the "principal depot for the east coast of Florida." During the Seminole Wars Fort Heilman was used as a quartermaster workshop and storage depot but was abandoned after the war in 1841. 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.
The 4th Massachusetts Cavalry had a small skirmish before raiding Middleburg during the American Civil War on October 23, 1864. The next day the 4th Massachusetts Cavalry set fire to a number of buildings and a hotel. The Federals retreated across Black Creek burning a bridge in the process. The 2nd Florida Cavalry caught up with the retreating 4th Massachusetts Cavalry in a skirmish at Halsey's Plantation.
The population numbered 700 in 1890. In 1895, a big freeze and lessening of the river trade caused the city to decline again.
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- "US Board on Geographic Names". United States Geological Survey. 2007-10-25. Retrieved 2008-01-31.
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