The Hollywood sign was officially dedicated in the hills above Los Angeles on July 13, 1923.
Originally reading "Hollywoodland", it was covered in 4000 light bulbs and intended as a short term advertisement for real estate. From the ground, the contours of the hills give the sign its wavy appearance, but from a comparable altitude, the letters appear to be level.
You can custom make your own Hollywood sign here. Handy tip for those sharing a home computer - why not make an obscene or offensive message for a family member, and leave it for them as a background image?