The El Dorado, AR Micropolitan Statistical Area includes all of Union County.

More recently, the city has been called "Arkansas's Original Boomtown," as it emphasizes its historic assets for heritage tourism.

[2] The chemical and timber industries became important during and after World War II, and still have a place in the economy.

Areas along the waterways were originally developed for cotton plantations in the antebellum years, and planters depended on large groups of enslaved African-American workers to generate their profits.

"[3] Oil production fell markedly in the early 1930s, in part due to companies' financial difficulties during the Great Depression.

The lowest point in the state of Arkansas, also the lowest point in all landlocked U.S. states, is located on the Ouachita River in Union County and Ashley County, where it flows out of Arkansas and into Louisiana.

As of the 2020 United States census, there were 39,054 people, 15,726 households, and 10,562 families residing in the county.

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.