The west end of US 66, at least in popular culture, has always been at the Pacific Ocean, or at least close to it. Santa Monica Pier, at times, touts itself as the western end. The intersection of Ocean Blvd and Santa Monica Blvd also does the same. While both are scenic and somewhat obvious ends, they simply are not correct.
As US 66 was by California standards, a State Highway, it falls under a specific standard. All signed routes, be they a State, US, or even Interstate Highway, ran along specified roadways which were all State Highways and maintained by the State. Signage for such routes would not have been on any other roadway, for a multitude of reasons. This may seem confusing to the layperson, but it does make sense. There is, as the saying goes, method to the madness. Think of it from a legal standpoint. If a highway is signed as a State, US, or Interstate route, the layperson (generally the public) would assume it be maintained by an agency above the city it passes through. Liability for such a roadway goes to the State. If the State has no interest in the roadway, there is no reason to push this perceived liability upon it. Therefore, only roadways maintained by the State get signed. Seems simple enough.
Now, how does this pertain to the western end of US 66 you ask? Both the pier and the intersection of Ocean and Santa Monica are not State Highways nor part of a State Highway The true end of the road was at a place that was far less extravagant and scenic. The end of US 66 was at the intersection of Lincoln Blvd and Olympic Blvd, which was the junction of US 66 (Lincoln Blvd north of Olympic), US 101 Alternate (Lincoln Blvd south of Olympic), and State Highway 26 (Olympic Blvd). Today, this intersection is at Lincoln Blvd, Olympic Blvd, and the Santa Monica Freeway. The western end of Olympic was subsumed by the Santa Monica Freeway (originally to be named the Olympic Freeway) in 1965. This western end existed from 1935 until 1964, when US 66 was cut back to Los Angeles.
Eventually, US 66 was cut back even further. Initially to Downtown Los Angeles, it was further reduced as time passed, and by 1984 the route was entirely gone. Today, the highway is marked by Historic Route signs across most of its journey through the Los Angeles area.
So, when visiting the west end of US 66, do it right. Visit the intersection of Lincoln Blvd and Olympic Blvd. Any other location is incorrect. If you do visit the pier, make sure to check out their exhibit on Bob Waldmire near the west end of Pacific Park, who helped promote old US 66 with his very intricate and detailed artwork.