Hempstead and Clark counties. The next spring, the county court convened at the former colonial trading post of Ecore Fabre (now Camden in Ouachita County) on a bluff overlooking the Ouachita River. Over the following two decades, three counties and parts of six others were carved from the original Union County. Areas along the waterways were originally developed for cotton plantations in the antebellum years.
Sources: The Encyclopedia of Arkansas History & Culture and Wikipedia
Ouachita, Calhoun, Bradley, Ashley and Columbia in addition to the Louisiana Parishes of Morehouse, Union and Claiborne.