- Founded (April 26, 1854)
- Proslavery settler Malcolm Clark killed (April 30, 1855)
- Law and Order Party founded (October 3, 1855)
- Unidentified antislavery German settler killed by Charles Fuget (August 19, 1856)
- Two proslavery men and one antislavery man killed (September 1, 1856)
- Leavenworth Constitution (May 18, 1858)
- Abraham Lincoln visits (December 1859)
Founded to the south of Fort Leavenworth by settlers from Weston, Missouri, the town of Leavenworth was the first city to be incorporated in Kansas. A majority of the residents maintained a proslavery stance during the Bleeding Kansas era, and it was the site of the founding of the proslavery Law and Order Party in 1855. On the other hand, Leavenworth lent its name to the Leavenworth Constitution, one of the most radically abolitionist of the proposed Kansas constitutions. Another less-publicized fact about Leavenworth in the Civil War era was the existence of a network of underground buildings and tunnels that were likely used as commercial facilities and in some cases as refuge for escaped slaves on the Underground Railroad. Today, the city limits of Leavenworth encompass Fort Leavenworth.