Kan. Stat. § 18-152
The county of Leavenworth is bounded as follows: Beginning at the southeast corner of Atchison county; thence west with the south boundary of Atchison county, to the corner of sections twenty-one, twenty-two, twenty-seven and twenty-eight, of township seven south, of range twenty east; thence south with the section lines between the third and fourth tiers of sections, to the middle of the main channel of the Kansas river; thence down said Kansas river, in the middle of the main channel thereof, to the intersection with the range line between ranges twenty-two and twenty-three east; thence north on said range line, to the old Delaware reserve line, the same being the dividing line between the original Delaware reservation and Delaware trust lands; thence east with said reserve line, to the western boundary line of the state of Missouri; thence northerly with said western boundary line of the state of Missouri, to the place of beginning.
K.S.A. 18-152