Although not an official holiday, as the birthday's of George Washington and Abraham Lincoln, today is the birthday of (IMHO) America's second-greatest Founder -- Alexander Hamilton (second only the Washington).
We know that Alexander Hamilton was born on January 11, but the year of his birth remains in dispute. Some contend that Hamilton was born in 1755, because a legal document, written after the death of Hamilton's mother, was located in the 20th century in the Caribbean Islands, where Hamilton was born, which speculated that he was born in 1755.
Alexander Hamilton himself always seemed to be of the opinion that he was born in 1757, because he calculated his age based upon that date in several documents he wrote.
But whatever year he was born, January 11 is definitely his birthday.
Happy Birthday, Alexander Hamilton. Your country has not yet forgotten you.
~President Calvin Coolidge, January 11, 1922~