Adjacent counties

• Washakie County – northeast
• Fremont County – south and southwest
• Park County – northwest and north

National protected area

• Shoshone National Forest (part)

2000 census

As of the 2000 United States Census,^[10] there were 4,882 people, 2,108 households, and 1,353 families in the county. The population density was 2 people per square mile (0.77 people/km²). There were 2,536 housing units at an average density of 1.3 units per square mile (0.50 units/km²). The racial makeup of the county was 95.96% White, 0.35% Black or African American, 1.52% Native American, 0.25% Asian, 0.63% from other races, and 1.29% from two or more races. 2.38% of the population were Hispanic or Latino of any race. 23.3% were of German, 17.0% English, 12.2% Irish, 8.2% American and 6.0% Norwegian ancestry.

There were 2,108 households, out of which 25.50% had children under the age of 18 living with them, 54.30% were married couples living together, 7.40% had a female householder with no husband present, and 35.80% were non-families. 31.70% of all households were made up of individuals, and 14.80% had someone living alone who was 65 years of age or older. The average household size was 2.25 and the average family size was 2.82.

The county population contained 22.00% under the age of 18, 5.90% from 18 to 24, 23.30% from 25 to 44, 28.70% from 45 to 64, and 20.00% who were 65 years of age or older. The median age was 44 years. For every 100 females there were 92.70 males. For every 100 females age 18 and over, there were 89.80 males.

The median income for a household in the county was $29,888, and the median income for a family was $39,364. Males had a median income of $27,030 versus $18,667 for females. The per capita income for the county was $16,858. About 8.60% of families and 10.60% of the population were below the poverty line, including 12.10% of those under age 18 and 7.90% of those age 65 or over.

2010 census

As of the 2010 United States Census, there were 4,812 people, 2,185 households, and 1,362 families in the county.^[11] The population density was 2.4 people per square mile (0.93 people/km²). There were 2,582 housing units at an average density of 1.3 units per square mile (0.50 units/km²).^[12] The racial makeup of the county was 95.8% white, 1.5% American Indian, 0.4% Asian, 0.2% black or African American, 0.1% Pacific islander, 0.5% from other races, and 1.5% from two or more races. Those of Hispanic or Latino origin made up 2.2% of the population.^[11] In terms of ancestry, 30.1% were German, 15.3% were Irish, 15.1% were English, 8.4% were Scotch-Irish, and 8.3% were American.^[13]

Of the 2,185 households, 23.5% had children under the age of 18 living with them, 50.5% were married couples living together, 8.3% had a female householder with no husband present, 37.7% were non-families, and 32.6% of all households were made up of individuals. The average household size was 2.16 and the average family size was 2.70. The median age was 48.6 years.^[11]

The median income for a household in the county was $42,469 and the median income for a family was $54,709. Males had a median income of $41,186 versus $26,990 for females. The per capita income for the county was $25,269. About 6.8% of families and 9.1% of the population were below the poverty line, including 12.2% of those under age 18 and 5.7% of those age 65 or over.^[14]

Towns

• East Thermopolis
• Kirby
• Thermopolis (county seat)

Census-designated places

• Lucerne
• Owl Creek

Unincorporated communities

• Embar^[15]
• Grass Creek
• Wedding of the Waters

Ghost Towns

• Gebo