In the colonial era the area that is now Aiken County was part of Edgefield and Orangeburgh Districts.

However, by the 1750s, almost all of the Lincolnshire settlers in what is now Aiken County were living on their own private land, almost exclusively engaging in subsistence agriculture on smallholding farms.

Specifically, many indentured servants came from the towns of Newark-on-Trent, Winthorpe, Coddington, Balderton, Kelham and Farndon.

A third group of English farmers settled in the colony, mostly arriving not as individual indentured servants but as entire family units, coming from the Derbyshire Dales region of the English county of Derbyshire; these settlers primarily originated in the three towns of Ashbourne, Bakewell and Matlock as well as the farm country surrounding these towns.

These settlers also settled on lands in between the Savannah River in the west and the towns of Berlin and Jones Crossroads in the east, all arriving in what has since become Aiken County in the 1740s.

This population referred to themselves as "Ulstermen" and "Irish Presbyterians" but were known in the colonies as "Scots-Irish" settlers, though this was not a term they self-applied.

[3][4][5][6] The area that has since become Aiken County had a significantly high number of first generation British immigrants who fought for the Patriot cause in the revolutionary war.

He was dubbed "The Black Prince" by local newspapers, including the Edgefield Advertiser.

He also led the commission that selected the site of Aiken County's present-day courthouse.

Other freedmen who were part of the founding of the county were Samuel J. Lee, speaker of the state House and the first black man admitted to the South Carolina Bar; and Charles D. Hayne, a free man of color from one of Charleston's elite families.

Between the Hamburg Massacre in July and several days of rioting in September in Ellenton, more than 100 black men were killed by white paramilitary groups in this county.

[10] In the late 19th century, the county became a popular winter refuge for affluent Northerners, who built luxury housing.

The county remains popular with horse trainers and professional riders because mild winters allow lengthy training seasons.

Its residents and businesses were moved north about eight miles to New Ellenton, and about 5 miles south to the town of Jackson just outside the entrance to the Savannah River Site, Developed during Cold War tensions, the facility is scheduled for decommissioning of various parts of the site.

It even rejected southern Democrats such as Lyndon Johnson of Texas, Jimmy Carter of Georgia, Bill Clinton of Arkansas or Al Gore of Tennessee.

However, it has trended more liberal in recent years, giving Bob Dole in 1996 a greater proportion of the vote than Donald Trump in 2016, despite Dole losing decisively to Bill Clinton nationally, and Donald Trump winning the Electoral College 304-227.

[33] As of April 2024[update], some of the largest employers in the county include Aiken Regional Medical Center, Bridgestone, Hubbell Incorporated, Kimberly-Clark, Savanah River Nuclear Solutions (SRNS), Shaw Industries, UPS, and Walmart.