[6] In the Nebraska license plate system, Polk County is represented by the prefix 41 (it had the 41st-largest number of vehicles registered in the county when the license plate system was established in 1922).

The Platte River flows northeastward along the northwest boundary of Polk County.

The county terrain consists of rolling hills, dropping off to the river valley in the northern portion, and sloped to the east-southeast in the lower portion of the county.

[9] As of the 2000 United States Census,[15] there were 5,639 people, 2,259 households, and 1,570 families in the county.

27.60% of all households were made up of individuals, and 15.40% had someone living alone who was 65 years of age or older.

In only one national election since 1936 has the county selected the Democratic Party candidate (as of 2024).