When Arkansas achieved statehood the same year as Texas declared itself an independent republic in 1836, a dispute arose over their common border, with the area in Miller County having representation in both the Arkansas legislature and the Texas congress.

Miller County is located in the southwest corner of Arkansas in the Piney Woods, a temperate coniferous forest.

Miller County is within the South Central Plains Level III ecoregion designated by the Environmental Protection Agency.

It contains frequently flooded forested wetlands, natural levees, swales, oxbow lakes, and meander scars.

Loblolly pine and oaks are common and are adapted to the prevailing hydroxeric regime; pastureland and hayland are less extensive.

They have more suspended solids, greater turbidity, and higher hardness values than the Tertiary Uplands.

The historic channel of the Red River defines the northern and eastern boundary of Miller County.

[13] Swamps and bayous along the Sulphur River drain much of the western part of Miller County.

[14] Areas within the levee are frequently subject to inundation by the Red, including a town evacuation of Garland City in 2015.

Within the WMA, 500 acres (200 ha) is maintained as the Henry Moore Waterfowl Rest Area.

All three high schools offer Advanced Placement (AP) courses and are accredited by the Arkansas Department of Education (ADE).

TPL offers books, e-books, media, reference, youth, business and genealogy services.

In Fouke, the Ann & Dewey Fowler Community Library is located at 305 N Snell Street in a restored Victorian house.

[35] The county's population is significantly above healthy weight, with 54.0% of adults and 38.0% of children/adolescents ranking as overweight or obese, compared to the state averages of 67.1% and 39.3%, respectively.

The agency is led by the Miller County Sheriff, an official elected by countywide vote every four years.

[41] Circuit court is held at the Miller County Courthouse at 400 Laurel Street in Texarkana.

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.

[42][43] Since the mid-20th century, Miller County has transitioned from reliably Democratic to steady Republican in national, state and local elections.

Miller County was part of the Solid South, a period of Democratic hegemony which began after Reconstruction following the Civil War.

The Solid South started to dissolve following the Civil Rights Act in 1964, which is when Miller County's streak of supporting Democratic candidates ended.

[44] In Congress, Arkansas has been represented by two Republican senators (John Boozman and Tom Cotton) since January 3, 2015, ending a long history of Democratic hegemony.

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

Due to Miller County's proximity to Texas, which has no state personal income tax, special taxation exemptions apply to residents with permanent addresses within the city limits of Texarkana.

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.

[51][52] The Arkansas Department of Health (ADH) is responsible for the regulation and oversight of public water systems throughout the state.

TWU, a joint department between the two Texarkana municipalities, provides drinking water and fire flows on both sides of the state line, including several partner cities in Texas.

[53] Miller County PWA purchases water from TWU, and has the same executive director as of February 2018.