In contrast, the northern portion of York County was considered part of North Carolina.

They comprised the most numerous immigrants from the British Isles in the eighteenth century and the latest to arrive.

Rising rent and land prices in western Pennsylvania drove them southward down the Great Wagon Road, and they began arriving in the Upcountry west of the Catawba River during the 1740s.

This area would remain a part of Tryon County until 1772 when the boundary between North and South Carolina in this portion was finally established.

Its boundaries remained unchanged until 1897 when a small portion of the northwestern corner (including the site of the Battle of Kings Mountain) was ceded to the newly formed Cherokee County, South Carolina.

By 1780, the Carolina Upcountry had an estimated population of more than 250,000, predominantly Scots-Irish Presbyterians but with significant numbers of other Protestants from Great Britain.

The Scots-Irish settled in a dispersed community pattern denoted by communal, clannish, family-related groups known as "clachans", much the same as in Pennsylvania and Ulster, Northern Ireland.

The local militia became an early police force, patrolling the area for possible Native American or enslaved rebellions and controlling the seemingly numerous outlaw bands that roamed the region.

The New Acquisition entered into vocal opposition to Royal authority in 1780 only after three "invasions" of the region: the first by Banastre Tarleton and his "Green Dragoons", and two more by Lord Cornwallis.

Still, after the Waxhaw massacre in nearby Lancaster County in May 1780, residents of the New Acquisition took part in a regional resistance.

In the years just before the Civil War, the town gained a reputation as a summer resort for many Lowcountry planters trying to escape the malarial swamps of the region for the more moderate climate to be found in the Upstate.

Slavery expanded significantly in York County between 1800 and 1860, with most enslaved on small and medium-sized farms rather than more extensive plantations.

On the eve of the American Civil War, the county's population had grown to approximately 21,500, with almost 1/2 enslaved laborers.

Chartered in 1848, the Kings Mountain Railroad Company began construction of a connecting line between Yorkville and the Charlotte and South Carolina Railway at Chester (completed in 1852).

Rock Hill, located along the Charlotte and South Carolina route, rapidly developed as a transportation center in eastern York County, boasting 100 residents in 1860.

The Kings Mountain Military Academy in Yorkville was the most famous, founded in 1854 by Micah Jenkins and Asbury Coward.

[6] There were 14 infantry companies formed in York County after South Carolina declared secession.

Between 1868 and 1871, York County became a hotbed of Ku Klux Klan attacks on African Americans.

[9] York is believed by some to be the setting for Thomas F. Dixon, Jr.'s novel The Clansman: A Historical Romance of the Ku Klux Klan, later made into the motion picture "The Birth of a Nation", and Bratton is said to have been the inspiration for one of its characters.

[10][11] During the Reconstruction era, many of York County's more prominent property owners were forced to sell portions of their land to smaller farmers.

Cotton production remained the dominant agricultural export in early 20th century York County, with the textile industry continuing to develop.

The New Deal programs of the 1930s prodded farmers into switching to different crops, with cotton gradually becoming less and less the focal point of the county's economy.

Construction began in 1900, and when it was finally completed, the dam and power plant were among the most important engineering accomplishments in the southeastern United States.

The venture eventually led to the formation of Duke Power Company,[12][13] and a later series of dams and hydroelectric facilities were built on the Catawba in both North and South Carolina.

Although heavily wooded in many rural areas and retaining a predominantly rural character in its western sector, York County is part of the Charlotte metropolitan area and includes Rock Hill, the county's largest city, as well as the smaller cities of Tega Cay and York and the smaller towns of Clover, Fort Mill, Hickory Grove, McConnells, Sharon, and Lake Wylie.

Henry's Knob, a mountain and site of a former open-pit mining operation for the world's largest deposit of kyanite stands at 1,120 ft (340 m) above sea level.

This was the best result for a Democrat since 1980 when Jimmy Carter received 50.2 percent of the vote and won York County.

[32] As of April 2024[update], some of the largest employers in the county include 7-Eleven, Bank of America, Continental AG, Food Lion, Meritor, Schaeffler Group, Walmart, and Wells Fargo.

York County is home to two free daily online newspapers that also print monthly newspapers, the YoCoNews that covers all of York and Lancaster counties, [34]and the Tega Cay Sun that covers Tega Cay and Fort Mill [35]