The county is named for Francis Marion, the famous "Swamp Fox" of the Revolutionary War.

[3] Located in the Ozarks, the county is largely covered with rugged terrain and waterways, with the exception of King's Prairie in the southwestern portion.

Protected areas of the county include Bull Shoals-White River State Park, Ozark National Forest, the Buffalo National River and four wildlife management areas (WMAs).

[4] Prior to white settlement, the Ozark Plateau was inhabited by the Osage Indians for centuries.

The territory was returned to France in 1800 and then sold to the United States as part of the Louisiana Purchase in 1803.

[6] As of the 2020 United States census, there were 16,826 people, 6,782 households, and 4,438 families residing in the county.

The quorum court is the legislative branch of the county government and controls all spending and revenue collection.

Representatives are called justices of the peace and are elected from county districts every even-numbered year.

[16][17] Over the past few election cycles Marion County has trended heavily towards the GOP.

This tax is collected by the Marion County Collector between the first business day of March of each year through October 15 without penalty.

Each township includes unincorporated areas; some may have incorporated cities or towns within part of their boundaries.

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.