[4] As of the 2020 United States census, there were 19,221 people, 8,243 households, and 5,672 families residing in the county.

There were 9,236 housing units at an average density of 11 per square mile (4.2/km2).

25.00% of all households were made up of individuals, and 12.30% had someone living alone who was 65 years of age or older.

Since 1952, Polk County has been heavily Republican, only voting for the Democratic nominee for president three times since then.

Polk County is the setting for Stephen Hunter's fictional Bob Lee Swagger series, the most notable being Black Light, as well as the place where Joel B Reed's fictional character, Jazz Phillips, of the Jazz Phillips mystery series, grew up.

Each township includes unincorporated areas; some may have incorporated cities or towns within part of their boundaries.

However, the United States census does list Arkansas population based on townships (sometimes referred to as "county subdivisions" or "minor civil divisions").

Each town or city is within one or more townships in an Arkansas county based on census maps and publications.