http://www.kclibrary.org/kchistory/annexation-wasn-t
In the 1870s, annexation supporters proposed a number of plans, several of which called upon Kansas to "purchase" the city from Missouri.
In 1878, The Kansas City Times began publishing articles in favor of annexation, arguing that the bulk of Kansas City’s trade already took place with towns in Kansas. Most Kansas City residents, according to the paper, considered themselves to be Kansans, regardless of the lines on a map. Furthermore, much of the area’s development was occurring in what would in 1886 become Kansas City, Kansas. The area’s emerging cities would essentially end up as one metropolis, yet the state line spurred economic and political divisions that could potentially impair growth on both sides. The Times articles reasoned that in consideration of Kansas City’s desire to be annexed, Missouri would agree to the plan, provided that it was allowed to retain all tax revenue from Kansas City for a period of 50 years.
This second movement for annexation culminated with the 1879 Kansas Senate resolution. The Kansas House voted in favor of the plan several days later, and the legislature awaited consent from Missouri and the U.S. Congress. It was the first time that the Kansas legislature officially attempted to annex Kansas City. Dozens of Kansas City business leaders and politicians pressed the Missouri legislature to concur with the resolution, but the city was now far more valuable than it had been in 1855 when Missouri was (according to Van Horn) willing to relinquish it. With no real incentive for Missouri to give up Kansas City, the Kansas-Missouri border remained stationary.
Further attempts to annex Kansas City occurred in 1884 and 1899. Throughout this time, Kansas City residents frequently claimed that surveyors failed to account for the changing routes of the Kansas and Missouri Rivers when determining the border. Therefore, the surveyors allegedly placed the Kansas-Missouri border six miles too far to the west in relation to the original Missouri state charter.