Sedalia is a city located approximately 30 miles (50 kilometers) south of the Missouri River and, as the county seat of Pettis County, Missouri, United States, it is the principal city of the Sedalia Micropolitan Statistical Area. As of the 2020 census, the city had a total population of 21,725. Sedalia is also the location of the Missouri State Fair and the Scott Joplin International Ragtime Festival. U.S. Routes 50 and 65 intersect in the city.

Indigenous peoples lived along the Missouri River and its tributaries for thousands of years before European contact. Historians believe the entire area around Sedalia was long occupied by the Osage (among historical American Indian tribes). When the land was first settled by European Americans, bands of Shawnee, who had migrated from east of the Mississippi River, lived in the vicinity of Sedalia.

Until the city was incorporated in 1860 as Sedalia, it had existed only "on paper" from November 30, 1857, to October 16, 1860. According to local lore, the town council changed the name from Sedville to Sedalia in part because "towns that end in -ville don't amount to anything." (Lawrence Ditton Sr.). Here is another account:

In 1856 General Smith bought the land upon which Sedalia now stands, and founded the city. He named it after his daughter Sarah, familiarly known as "Sed". Smith remarked that he had previously named a flatboat for her elder sister Martha. He first chose the name Sedville but changed it to Sedalia, following the suggestion of a friend, Josiah Dent, of St. Louis. Dent suggested the change for the sake of euphony.

The area that became the European-American city of Sedalia was founded by General George Rappeen Smith (1804–1879), who also founded nearby Smithton, Missouri. He filed plans for the official record on November 30, 1857, and gave the area the name Sedville. The original plat included the land from today's Missouri Pacific Railroad south to Third Street.

The version jointly filed by General Smith and David W. Bouldin on October 16, 1860, displayed the city extending from Clay Street to the north and to Smith Street (today's Third Street) in the south, and from Missouri Street in the west to Washington Street in the east; and, although Smith and Bouldin predicted that the city would grow to the north, it grew in a southern direction.

Following a victory for those proposing the "ridge route" for the railway over those advocating the "river route", the railway reached Sedalia in January 1861. Sedalia's early prosperity was directly related to the railroad industry. Many jobs were associated with men maintaining tracks and operating large and varied machine shops run by both the Missouri Pacific and the Missouri-Kansas-Texas Railroad lines. The Missouri-Kansas & Texas Railroad was widely known as the "KATY", from its "K-T" stock exchange code.

Sedalia was an important railhead for the massive Texas cattle drive of 1866. It maintained stockyards to receive cattle from drives and shipping through much of the 19th century.