Minn. Stat. § 161.139: HIGHWAY DESIGNATION COSTS.

The commissioner shall not adopt a design or erect a sign to mark or memorialize a highway or bridge, pursuant to designation by the legislature, unless the commissioner is assured of the availability of funds from nonstate sources sufficient to pay all costs related to designing, erecting, and maintaining the signs. The commissioner may remove a sign that marks or memorializes a highway or bridge as designated by the legislature if:

(1) the sign requires maintenance, repair, or replacement;

(2) the commissioner has made a reasonable effort to obtain funds for maintenance, repair, or replacement from nonstate sources; and

(3) the funds obtained under clause (2) are insufficient to pay all related costs.