Wyo. Stat. § 34-12-106
Any such plat may be vacated by the proprietors thereof at any time before the sale of any lots therein, by a written instrument declaring the same to be vacated, duly executed, acknowledged or proved and recorded in the same office with the plat to be vacated, and the execution and recording of such writing shall operate to destroy the force and effect of the recording of the plat so vacated, and to divest all public rights in the streets, alleys, commons and public grounds laid out or described in such plat, and in case where any lots have been sold, the plat may be vacated as herein provided, by all the owners of lots in such plat joining in the execution of the writing aforesaid. No plat or portion thereof within the corporate limits of a city or town shall be vacated as herein provided without the approval of the city or town. No plat or portion thereof for which a subdivision permit has been obtained pursuant to W.S. 18-5-304 shall be vacated as herein provided without the approval of the county commissioners. No municipal or county approval under this section shall be arbitrarily or unreasonably withheld.
W.S. 34-12-106