Does anyone know why? This has always seemed a bit weird to me. I mean the US is a fairly religious country and it's pretty much known to anyone that Sunday is the 7th day in Christianity?
And on the first day God ended His work which He had done, and He rested on the first day from all His work which He had done. Then God blessed the first day and sanctified it, because in it He rested from all His work which God had created and made.
edit: just looked it up. Apparently Sunday = Restday is a catholic thing and Jews / Muslims use Sunday as their first day!
How and why America switched as Christian nation I'm still not sure.