As an Aussie who’s relatively new to the US, I’ve been really confused on more than one occasion about the seemingly “optional” nature of US Public Holidays. While there seems to be something every month that is enough to shut down the Post Office and occasionally the bank, there are actually only a few of these public holidays where it is customary for “normal businesses” to close for the day.
Of course, getting a list of the “real” holidays vs the government worker holidays is a bit like that line from “A Few Good Men” when Lt Kaffee (Tom Cruise) asks Cpl Barnes (Noah Wyle) where the mess hall is in the official Marine Corps manual: “I guess I just followed the crowd at chow time, Sir”.
Of course, this creates a few problems if you’re trying to manage a team and you don’t know where to lead them at chow time. So, here’s the list I’ve been able to compile of the “real” holidays in the US in the process of building AffinityLive:
Yep, that’s it. President’s Day, Martin Luther King Day, Columbus Day, Veteran’s Day and all manner of other magic days aren’t days where you’d call your lawyer, accountant or other professional/office type business and expect to get a “we’re not here – it is a holiday” response.
geoffmcqueen.com 
Having lived in the US for 5 years in the 1960s I recognise the confusion. Different states celebrate different holidays. For example Lincoln’s birthday is an important calendar day in Illinois! I agree with you about the 6 key dates for public holidays. I seem to remember that employees of the Christian faith are allowed 2 hours off on Good Friday to go to church, but otherwise Easter goes uncelebrated. When I was there, most employers gave 10 public holidays each year, those 6 plus 4 others. Sometimes the others were tacked on to the main public holidays – like the Friday after Thanksgiving. Sometimes they were state based holidays.
Enjoy your time in the US Geoff. Isn’t San Francisco a great city to live in? I lived there for 2 years in the ‘flower children’ days and still have many friends in California, most living outside the city because of the high cost of living for retirees.