California Code, Streets and Highways Code - SHC § 660

(a) Highway.  “Highway” includes all, or any part, of the entire width of the right-of-way of a state highway, whether or not the entire area is actually used for highway purposes.

(b) Encroachment.  “Encroachment” includes any tower, pole, pole line, pipe, pipe line, fence, billboard, stand or building, or any structure, object of any kind or character not particularly mentioned in this section, or special event, which is in, under, or over any portion of the highway.  “Special event” means any street festival, sidewalk sale, community-sponsored activity, or community-approved activity.