(1) No sign lawfully erected in a protected area as defined by section 2, chapter 96, Laws of 1961 (before the amendment thereof), prior to March 11, 1961, within a commercial or industrial zone within the boundaries of any city or town, as such boundaries existed on September 21, 1959, wherein the use of real property adjacent to the interstate system is subject to municipal regulation or control but which does not comply with the provisions of this chapter or any regulations promulgated hereunder, shall be maintained by any person after March 11, 1965.

(2) No sign lawfully erected in a protected area as defined by section 2, chapter 96, Laws of 1961 (before the amendment thereof), prior to March 11, 1961, other than within a commercial or industrial zone within the boundaries of a city or town as such boundaries existed on September 21, 1959, wherein the use of real property adjacent to the interstate system is subject to municipal regulation or control but which does not comply with the provisions of this chapter or any regulations promulgated hereunder, shall be maintained by any person after three years from March 11, 1961.

(3) No sign lawfully erected in a scenic area as defined by section 2, chapter 96, Laws of 1961 (before the amendment thereof), prior to the effective date of the designation of such area as a scenic area shall be maintained by any person after three years from the effective date of the designation of any such area as a scenic area.

(4) No sign visible from the main traveled way of the interstate system, the primary system (other than type 3 signs along any portion of the primary system within an incorporated city or town or within a commercial or industrial area), or the scenic system which was there lawfully maintained immediately prior to May 10, 1971, but which does not comply with the provisions of chapter 47.42 RCW as now or hereafter amended, shall be maintained by any person (a) after three years from May 10, 1971, or (b) with respect to any highway hereafter designated by the legislature as a part of the scenic system, after three years from the effective date of the designation. Signs located in areas zoned by the governing county for predominantly commercial or industrial uses, that do not have development visible to the highway, as determined by the department, and that were lawfully installed after May 10, 1971, visible to any highway now or hereafter designated by the legislature as part of the scenic system, shall be allowed to be maintained.