The first petrochemical plant in the world was built in Clendenin in 1920. This plant was the original Union Carbide Corporation facility. Other chief economic staples included (and to some extent still include) timber, coal, gas, oil, and salt.
In the 1960s, the hillside on the south side of town featured a sign reading, "Clendenin's Beauty is Everyone's Duty".
The current mayor of Clendenin is Mayor Robert Ore. Town elections (including the office of mayor and city council) occur every two years. Recent efforts have been made by the Business and Industrial Development Corporation (headquartered in Charleston) to enhance economic and cultural development in the town.
As of the census of 2000, there were 1,116 people, 475 households, and 326 families residing in the town. The population density was 324.0/km² (838.8/mi²). There were 525 housing units at an average density of 152.4/km² (394.6/mi²). The racial makeup of the town was 99.01% White, 0.09% African American, 0.09% Native American, 0.09% Asian, and 0.72% from two or more races. Hispanic or Latino of any race were 0.18% of the population.
There were 475 households out of which 24.8% had children under the age of 18 living with them, 53.1% were married couples living together, 10.3% had a female householder with no husband present, and 31.2% were non-families. 27.4% of all households were made up of individuals and 15.2% had someone living alone who was 65 years of age or older. The average household size was 2.32 and the average family size was 2.80.
In the town the population was spread out with 20.3% under the age of 18, 6.7% from 18 to 24, 28.0% from 25 to 44, 25.7% from 45 to 64, and 19.3% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 89.5 males. For every 100 females age 18 and over, there were 85.4 males.
The median income for a household in the town was $32,000, and the median income for a family was $38,021. Males had a median income of $30,000 versus $18,500 for females. The per capita income for the town was $16,587. About 9.7% of families and 14.6% of the population were below the poverty line, including 13.7% of those under age 18 and 20.2% of those age 65 or over.