Tornado

On November 10, 2002, a tornado destroyed 50 homes. At least seven people were killed in the Morgan County communities of Mossy Grove and Joyner.

Adjacent counties

• Scott County (northeast)
• Anderson County (east)
• Roane County (south)
• Cumberland County (southwest/CST Border)
• Fentress County (northwest/CST Border)

National protected areas

• Big South Fork National River and Recreation Area (part)
• Obed Wild and Scenic River (part)

State protected areas

• Catoosa Wildlife Management Area (part)
• Frozen Head State Natural Area
• Frozen Head State Park
• Justin P. Wilson Cumberland Trail State Park
• Lone Mountain State Forest
• North Cumberland Wildlife Management Area (part)
• Rugby State Natural Area

2020 census

As of the 2020 United States census, there were 21,035 people, 7,625 households, and 5,659 families residing in the county.

2000 census

As of the census^[13] of 2000, there were 19,757 people, 6,990 households, and 5,235 families residing in the county. The population density was 38 people per square mile (15 people/km²). There were 7,714 housing units at an average density of 15 units per square mile (5.8/km²). The racial makeup of the county was 96.72% White, 2.23% Black or African American, 0.20% Native American, 0.12% Asian, 0.01% Pacific Islander, 0.14% from other races, and 0.59% from two or more races. 0.61% of the population were Hispanic or Latino of any race.

There were 6,990 households, out of which 33.50% had children under the age of 18 living with them, 60.70% were married couples living together, 10.30% had a female householder with no husband present, and 25.10% were non-families. 22.10% of all households were made up of individuals, and 9.30% had someone living alone who was 65 years of age or older. The average household size was 2.58 and the average family size was 3.01.

In the county, the population was spread out, with 23.20% under the age of 18, 8.80% from 18 to 24, 31.90% from 25 to 44, 24.50% from 45 to 64, and 11.50% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 114.30 males. For every 100 females age 18 and over, there were 116.40 males.

The median income for a household in the county was $27,712, and the median income for a family was $31,901. Males had a median income of $25,683 versus $18,606 for females. The per capita income for the county was $12,925. About 13.50% of families and 16.00% of the population were below the poverty line, including 18.50% of those under age 18 and 15.80% of those age 65 or over.

Cities

• Harriman (mostly in Roane County)
• Sunbright
• Wartburg (seat)

Towns

• Oakdale
• Oliver Springs (part)

Census-designated places

• Coalfield
• Petros

Unincorporated communities

• Annadel
• Deer Lodge
• Joyner
• Lancing
• Midway
• Rugby (partial)
• Shady Grove