Arkadelphia is a city in Clark County, Arkansas, United States. As of the 2020 census, the population was 10,380. The city is the county seat of Clark County. It is situated at the foothills of the Ouachita Mountains. Two universities, Henderson State University and Ouachita Baptist University, are located here. Arkadelphia was incorporated in 1857.
The site was settled in about 1809 by John Hemphill, operator of a nearby salt works, Arkansas's first industry. It was known as Blakelytown until 1839, when the settlement adopted the name Arkadelphia. The town was named "Arkadelphia," a portmanteau of Ark- from the state's name Arkansas and adelphia from the Greek meaning "brother/place".
Arkadelphia was once known as the "City of Rainbows", perhaps because the humid climate often resulted in rain.
Arkadelphia is located in northeastern Clark County at (34.121920, -93.066178), on the west bank of the Ouachita River. According to the United States Census Bureau, the city has a total area of , of which is land and , or 0.49%, is water.
The climate is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen climate classification system, Arkadelphia has a humid subtropical climate, abbreviated "Cfa" on climate maps.
As of the 2020 United States census, there were 10,380 people, 3,751 households, and 1,966 families residing in the city.
As of the 2010 United States Census, there were 10,714 people living in the city. The racial makeup of the city was 64.0% White, 30.0% Black, 0.4% Native American, 0.8% Asian,