The container cranes at the Port of Oakland are part legend, part myth, primarily centered around an urban myth that they insipred the AT-ATs in “The Empire Strikes Back”. Star Wars creator and Local Bay Area resident George Lucas has denied this myth on many occassions.
The famed Star Wars AT-ATs (“All Terrain Armored Transports”) are described by Wookieepedia as:
The All Terrain Armored Transport (AT-AT) walker, also known as the Imperial Walker, was a major part of the Galactic Empire’s army. It was one of the most heavily armored land vehicles in the Imperial Army, but was also known for its relatively slow speed.