California Code, Business and Professions Code - BPC § 5410

Any advertising display located within 660 feet of the edge of the right-of-way of, and the copy of which is visible from, any penalty segment, or any bonus segment described in Section 5406 which display was lawfully maintained in existence on the effective date of this section but which was not on that date in conformity with the provisions of this article, may be maintained, and shall not be required to be removed until July 1, 1970.  Any other sign which is lawful when erected, but which does not on January 1, 1968, or any time thereafter, conform to the provisions of this article, may be maintained, and shall not be required to be removed, until the end of the fifth year after it becomes nonconforming;  provided that this section shall not apply to advertising displays adjacent to a landscaped freeway.