FYI -- Muir Woods is nice, but I actually find the redwood groves in and around the town of Mill Valley to be nicer. So... If Muir Woods isn't open, just park your car in Mill Valley downtown and walk to Old Mill Park and Cascade Drive.
You might want to double check because they're open on federal holidays too, and New Years is that holiday where many national parks are packed. You'll have to reserve a parking arrival time online in addition to park entry fee. Ask if it is free though, because all national parks should be free on federal holidays but they charged me on Thanksgiving day. Best of luck!
Due Christmas Timings it may be closed.
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