Lemhi County is a county located in the U.S. state of Idaho. The county was established in 1869. It was named after Fort Lemhi. As of the 2000 Census the county had a population of 7,806 (2005 estimate: 7,909) The county seat is Salmon.
There were 3,275 households out of which 28.60% had children under the age of 18 living with them, 57.80% were married couples living together, 6.90% had a female householder with no husband present, and 32.30% were non-families. 27.70% of all households were made up of individuals and 12.40% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 2.91.
In the county the population was spread out with 25.50% under the age of 18, 5.50% from 18 to 24, 22.70% from 25 to 44, 29.50% from 45 to 64, and 16.80% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 99.20 males. For every 100 females age 18 and over, there were 97.50 males.
The median income for a household in the county was $30,185, and the median income for a family was $35,261. Males had a median income of $30,558 versus $18,289 for females. The per capita income for the county was $16,037. About 10.60% of families and 15.30% of the population were below the poverty line, including 19.80% of those under age 18 and 10.30% of those age 65 or over.