If, as a result of such required surveys, maps and estimates, the Secretary of the Interior shall be satisfied that one or more desirable parkway routes are available, then the state transportation department of this state be and it hereby is authorized to accept donations of and acquire lands, interests in lands, islands, waters, easements and other property and thereafter convey same to the United States on behalf of this state, or such of its political subdivisions or private parties may convey necessary or convenient property or easements for such projected parkway, together with sites in connection therewith acquired or to be acquired for recreational or naturalistic purposes. Thereafter, such areas shall constitute such national parkway in this state.