[2] The county was organized on January 24, 1833, and named after former U.S. Representative Spencer Darwin Pettis.

Pettis County comprises the Sedalia, MO Micropolitan Statistical Area.

The county is home to the site of the Missouri State Fair in Sedalia.

The Republican Party predominantly controls politics at the local level in Pettis County.

Pettis County is divided into four legislative districts in the Missouri House of Representatives, all of which are held by Republicans.