Almost the furthest west you can possibly go in California, it's the lost coast of California, where the Mattole river meets the sea
Cape Mendocino is not far away from here but it's not the westernmost place in the continental USA. Cape Alava, Washington is or Cape Blanco in Oregon, depending on how high the tide is. Seems to be quite the controversy. Either way, all three of these places are about as far west as you're going to go without a boat