Minn. Stat. § 161.29

On determining that it is in the best interests of the public and necessary in the location, construction, improvement, or maintenance of any trunk highway, the commissioner may designate by order as a part of the trunk highway system any toll bridge situated wholly within the state, and may acquire by purchase, gift, or condemnation, as provided by law, the necessary rights or easement in, to, or over any such toll bridge as will enable the public to use the bridge for highway traffic free of toll.