Lincoln County is included in the Hailey, ID Micropolitan Statistical Area.

[5] As of the census[12] of 2000, there were 4,044 people, 1,447 households, and 1,050 families living in the county.

22.90% of all households were made up of individuals, and 10.20% had someone living alone who was 65 years of age or older.

Out of the total population, 18.30% of those under the age of 18 and 7.00% of those 65 and older were living below the poverty line.

As of the 2010 United States Census, there were 5,208 people, 1,705 households, and 1,271 families living in the county.

[14] The racial makeup of the county was 80.1% white, 0.7% American Indian, 0.4% black or African American, 0.4% Asian, 0.1% Pacific islander, 16.2% from other races, and 2.2% from two or more races.

[13] In terms of ancestry, 21.2% were German, 17.3% were English, 6.9% were Irish, and 6.1% were American.

[16] As of the 2020 United States Census, there were 5,127 people and 1,804 households living in the county.

School districts include:[19] The county is in the catchment area, but not the taxation zone, for College of Southern Idaho.