Henryetta is a city in Okmulgee County, Oklahoma, United States. The population was 5,640 at the 2020 census. Hugh Henry established a …Henryetta is a city in Okmulgee County, Oklahoma, United States. The population was 5,640 at the 2020 census. Hugh Henry established a ranch on Creek Nation land in 1885. He soon found a deposit of coal, which he began using to fuel the forge at his ranch. Discovery of more coal deposits in the large Henryetta Coal Formation attracted several railroads to develop these mines. A settlement named Furrs grew up around the mines. The name changed to Henryetta when a post office opened on August 28, 1900.