Technically, February 15th is the birthday observance day for George Washington, our first president. George Washington was born on February 22, 1732, but with the adoption of the Monday Holiday Law (which created a uniform system of federal Monday holidays), his birthday celebration was moved to the third Monday in February. Eventually, today became known as President's Day, and is actually held in honor of both Washington and Abraham Lincoln (born February 12th). Recently, President's Day has been regarded as a day to honor all former presidents of the United States.
Check out the White House's site for more information on all presidents of the United States: http://www.whitehouse.gov/about/presidents/
And if you missed Lincoln's birthday last Friday, you might be interested in exporing the Abraham Lincoln digital archive available from the State of Illinois: http://www.idaillinois.org/cdm4/browse.php?CISOROOT=%2Fisl6
* the above information can be found in the 2010 Chase's Calendar of Events, kept behind the Richardson Library reference desk