The department shall maintain in the office of the tax assessor for each of the several counties a copy of all highway plans on which are indicated the widths of the rights-of-way for each road in the related district or county and an alphabetical list of property owners on each road for which rights-of-way have been acquired. These records must be for the convenience of persons making inquiry as to the right of the State in and to the right-of-way for roads constructed by the department in any county. The tax assessors of the several counties shall cooperate with the department in keeping these records current, without charge.