- Sedalia is a city located in Pettis County, Missouri, United States. It is the county seat of Pettis County and has a population of approximately 21,750 people as of the 2010 census. Sedalia is known for hosting the Missouri State Fair, which takes place annually in August and showcases agricultural exhibits, live entertainment, and various attractions. The city is also home to the historic Katy Depot, a train station turned museum, and the Daum Museum of Contemporary Art. Sedalia offers a variety of recreational opportunities, including parks, trails, and sports facilities. The city has a rich history in agriculture, railroads, and the arts, contributing to its vibrant cultural scene.