The portion of United States highway 81 where it enters the state on the Kansas-Nebraska line on the north thence south to the junction of interstate highway I-70 is hereby designated the Frank Carlson memorial highway. The secretary of transportation shall place suitable signs along the highway right-of-way at proper intervals to indicate the highway is the Frank Carlson memorial highway. The secretary of transportation may accept and administer gifts and donations to aid in obtaining suitable highway signs.