United States highway 166 where it enters the city of Coffeyville on the northeast, thence south and west through the city to the point where it exits the city of Coffeyville on the west, is hereby designated as the Martin Luther King, Jr. memorial highway. The secretary of transportation shall place signs along the highway right-of-way at proper intervals to indicate that the highway is the Martin Luther King, Jr. memorial highway. The secretary of transportation may accept and administer gifts and donations to aid in obtaining and installing suitable highway signs.