The histories of Kansas City, Kansas and Kansas City, Missouri are inextricably linked, having been created from the same original township and only becoming divided some twenty years after its founding.

In 1821, Frenchman Francois Gesseau Chouteau set up a trading post at the junction of the Missouri and Kansas Rivers, which he named, "the village of the Kansa," after a local Native American tribe. It would not be until 1833, however, until any semblance of a city was formed in what is today the Westport neighborhood of Kansas City, Missouri. In 1838, a group of local merchants formed the "Town of Kansas Company," by the junction and the following year the Westport area was renamed the Town of Kansas.

With the westward expansion of the United States, the Town of Kansas became an important point in the trail west. Indeed, Kansas was the only subsantially-populated town between St. Lois and California. In 1850, the Town of Kansas was incorporated into Missouri and the name was changed to the City of Kansas.

In those times, Missouri was a slave state. However, directly next to Kansas City was the Kansas Territory, which was heretofore a free territory. With the passage of the Kansas-Nebraska Act of 1854, Kansans were allowed to decide whether they wished to become slave or free. Many Missourians supporting slavery entered Kansas from the City to elect a pro-slavery Kansas Territorial Legislature into office. In response, abolitionists declared the legislature void and elected their own slate of representatives for a newly-formed legislature. After the legislature and township was burned by slavery supporters, the famous abolitionist John Brown entered Kansas City, freeing slaves and burning nearby plantations, sparking off a series of border wars known as Bleeding Kansas and regarded as some as the opening salvo of the Civil War. President James Buchanan had to send in federal troops to keep the peace.

During the Civil War, Kansas was on the side of the Union, but Missouri was not. On October 22 and 23, Confederate and Union troops fought a fierce battle in the City of Kansas and Wesport known as the Battle of Westport; the Unions troops won and pushed the Conferedacy out of Missouri into Arkansas.

In 1889, the City of Kansas officially changed its name to Kansas City and in 1897, it annexed Westport.

Today, Kansas City is the second-largest railroad hub in the United States and is home to the country's first shopping center, the Country Club Plaza (located in KC, Missouri).