According to the United States Census Bureau, the city has a total area of, of which is land and is water. Garnett is famous for its fossil finds from the late Carboniferous period. The lagerstätte is about 300 million years old and contains some of the earliest reptiles on earth.
As of the census of 2010, there were 3,415 people, 1,419 households, and 862 families living in the city. The population density was. There were 1,591 housing units at an average density of. The racial makeup of the city was 96.7% White, 0.4% African American, 0.6% Native American, 0.5% Asian, 0.6% from other races, and 1.3% from two or more races. Hispanic or Latino of any race were 2.1% of the population. There were 1,419 households of which 30.0% had children under the age of 18 living with them, 45.5% were married couplesliving together, 10.4% had a female householder with no husband present, 4.9% had a male householder with no wife present, and 39.3% were non-families. 34.0% of all households were made up of individuals and 19.4% had someone living alone who was 65 years of age or older. The average household size was 2.33 and the average family size was 2.98. The median age in the city was 40.9 years. 25.1% of residents were under the age of 18; 7.7% were between the ages of 18 and 24; 21.7% were from 25 to 44; 23% were from 45 to 64; and 22.5% were 65 years of age or older. The gender makeup of the city was 47.9% male and 52.1% female.
2000 census
As of the census of 2000, there were 3,368 people, 1,439 households, and 886 families living in the city. The population density was 1,124.6 people per square mile. There were 1,597 housing units at an average density of 533.2 per square mile. The racial makeup of the city was 96.97% White, 0.39% African American, 1.04% Native American, 0.27% Asian, 0.06% Pacific Islander, 0.53% from other races, and 0.74% from two or more races. Hispanic or Latino of any race were 1.45% of the population. There were 1,439 households out of which 28.8% had children under the age of 18 living with them, 50.2% were married couples living together, 8.5% had a female householder with no husband present, and 38.4% were non-families. 34.7% of all households were made up of individuals and 21.1% 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 2.91. In the city, the population was spread out with 24.4% under the age of 18, 7.5% from 18 to 24, 23.3% from 25 to 44, 20.7% from 45 to 64, and 24.1% who were 65 years of age or older. The median age was 41 years. For every 100 females, there were 88.2 males. For every 100 females age 18 and over, there were 82.1 males. The median income for a household in the city was $31,518, and the median income for a family was $38,095. Males had a median income of $31,175 versus $19,858 for females. The per capita income for the city was $16,265. About 9.2% of families and 13.0% of the population were below the poverty line, including 18.6% of those under age 18 and 9.9% of those age 65 or over.
The area has one railroad, six freight lines and six interstate carriers.
Roads
Garnett is at the crossroads of U.S. Route 59, U.S. Route 169 and K-31. Interstate 35 is located 19 miles north of here and Interstate 70 is approximately 50 miles away.
Air
The Garnett Industrial Airport is located along U.S. 169. The nearest international air service is at the Kansas City International Airport, 90 miles away.
