It's officially named Washington's Birthday. Lincoln's birthday is, I think, the same week, so people unofficially named it President's Day back in the eighties for publicity's sake (President's day sales and such). I don't like this, because Washington was the single most important man in the history of this nation. Nothing against Jesus or MLK, but if people in this country should be celebrating anyone's birthday, it's his. You can not stress enough the continuing importance of George Washington to even the modern US.
That said, there should be no holidays. They suck. Employees should just get a mandatory week of vacation per year so we can forget about all the disruptions.