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Ouachita Mountains

Last updated: July 3rd, 2026

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Name	†	Color on Map	EPA Code‡
Athens Plateau	○		36a
Central Mountain Ranges	○		36b
Central Hills, Ridges, and Valleys	○		36c
Fourche Mountains	○		36d
Western Ouachitas	○		36e
Western Ouachita Valleys	○		36f

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

‡ This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.

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↑About the Ouachita Mountains

The Ouachita Mountains are a small east-west mountain range extending from Eastern Oklahoma into Western Arkansas, located to the south of the Arkansas Valley.

The climate is humid and subtropical, with an asymmetrical, weakly-bimodal pattern of precipitation: spring and fall are both wetter, and summer and winter drier, but the spring wet season tends to be longer and more intense than the fall wet season. This seasonality of precipitation is subtle and in most years there is ample precipitation year-round, although prolonged droughts are possible at any time of year.

The topography here consists of open high hills and low mountains, mostly arranged along east-west ridges. The terrain is mostly formed of compressed sedimentary rock which has folded and faulted in places, and more recently, been heavily eroded by water. Valleys tend to be narrow. The most common rocks are sandstone and shale, both of which form acidic, nutrient-poor surface soils, but there are local pockets of richer soil. Streams tend to be perennial and high-to-moderate-gradient; there are some springs.

This region was historically covered in oak-hickory-pine forests. Nowadays, owing primarily to forestry plantations, loblolly pine and shortleaf pine are dominant. Oaks and hickories are still somewhat common, although less so than historically: dominant species include southern red oak (Quercus falcata), black oak (Quercus velutina), post oak (Quercus stellata), white oak (Quercus alba), and various hickories (Carya sp.)

The dominant land use here is commercial forestry; there is some grazing, pastureland, hay production, and some broiler chicken farming. There is some outdoor recreation, and this use has been increasing recently. Hot Springs, AR is the largest city here.

This region is bordered to the north along its entire length by the Arkansas Valley, which is mostly lower-elevation but has isolated areas that reach to higher elevations than here. In the east of this region, the Arkansas River Floodplain cuts a narrow channel through these mountains as it flows southeast to join the Mississippi. The border to the south is mostly with the South Central Plains (Piney Woods), a region of lower elevation and rainfall where pines are now dominant. At the far east of this region, however, there is a small border to the southeast with the Mississippi Alluvial Plain, locally called "the delta", a low, swampy area along the Mississippi river.

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