Mo. Rev. Stat. § 233.095

Said board shall have authority to expend not more than one-fourth of the revenue which may now or which may hereafter be paid into its treasury for the purpose of grading and repairing any roads or streets within the corporate limits of any city within said special road district in conformity with the established grade of said roads and streets in said cities and for the purpose of constructing and maintaining macadam, gravel, rock or paved roads or streets within the corporate limits of any city within the said special road district in conformity with the established grade of said roads and streets in said city; provided, that no part of the revenue of any special road district in this state be expended outside of the county in which such special road district is situated.