The county is named for Edward Hempstead, a delegate to the U.S. Congress from the Missouri Territory, which included present-day Arkansas at the time.

The 42nd United States President, Bill Clinton, who served from 1993 to 2001, was born in the county seat of Hope on August 19, 1946.

As of the 2020 United States census, there were 20,065 people, 8,094 households, and 5,711 families residing in the county.

Starting in 2008, voters of Hempstead County have shifted to the political right in US presidential elections.

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.