Kan. Stat. § 19-4303
Any county designated as an urban area county by the legislature pursuant to the provisions of section 17 of article 2 of the constitution of the state of Kansas and any county having a population of more than three hundred thousand (300,000) and any county having a population of more than sixty-five thousand (65,000) and less than one hundred eighty thousand (180,000) shall be subject to the provisions of this act. Any county having a population of more than forty-five thousand (45,000) and less than one hundred thousand (100,000) and in which there is located an active military establishment may be subject to the provisions of this act upon the adoption of a resolution by the board of county commissioners of such county, electing to be subject to the provisions of this act.
K.S.A. 19-4303