Ancient Indigenous peoples occupied areas along the waterways for thousands of years prior to European exploration.

[3] Settlers in the 19th century found earthwork mounds, 10 to 15 feet in height, in areas around what developed as Arkadelphia, Arkansas.

[4] At the time of European-American settlement after the United States acquired this territory in the Louisiana Purchase of 1803, the pioneers encountered three major Native American tribes: the Caddo, who lived along the banks of the Caddo River; the Quapaw on the Ouachita River, for several miles below what is now Arkadelphia; and the Lenape (known then as Delaware, who were driven to this area by European pressure from the mid-Atlantic East Coast) along the lower Ouachita to below present-day Camden.

The county is named after William Clark, then Governor of the Missouri Territory, which included present-day Arkansas.

Three of the six lynchings recorded in Clark County from 1877 to 1950[5] took place in a mass event in late January 1879.

Daniels and two of his sons were forcibly taken out of the jail by a white mob and lynched by hanging from trees in the courthouse square, without trial.

The cotton culture had been affected by the invasion of the boll weevil, which attacked the plants; and mechanization of agriculture, reducing the need for workers.

In this period, many African-American families, who still constituted most of the farm workers, also left Arkansas and other parts of the rural South to escape Jim Crow oppression and seek better employment in Northern and Midwestern cities in the Great Migration.

In the latter part of this period, some migrated to the West Coast, where the defense industry developed during and after World War II offered higher paying jobs.

Several companies had operated sawmills and related businesses in Clark County in the early part of the century.

In the 1970s, the DeGray Dam and Lake were completed along the Caddo River, providing new areas in the county for tourism and recreation, which have become major components of the economy.

[18][19] All three seats are held by Republicans Justin Gonzales, Richard Womack, and Steve Crowell, respectively.

[20][21] Republicans hold every county-wide office except the Sheriff and Collector, and have a seven-to-four super-majority on the Quorum Court.

However, the United States census does list Arkansas population based on townships (sometimes referred to as "county subdivisions" or "minor civil divisions").

Each town or city is within one or more townships in an Arkansas county based on census maps and publications.