The "summit" of Mt. Wilson is rather anti-climatic. It's a broad area with no well-defined peak. There are several telescopes and a large number of television and radio antennae. Really I would describe this as more of the Mt. Wilson "complex," complete with roads, cars, and buildings.
It can be tricky to find your way through the complex. Follow the road that dissects the facility, heading west. You'll find the old visitor center and the broad gravel lot where the real trail resumes.