Originally this was to celebrate the birthday of George Washington.
Abraham Lincoln's birthday was also celebrated on February 12, in the NORTHERN part of the country; while the birthday of Robert E. Lee was celebrated in the SOUTHERN part of the country.
But when a holiday was added to celebrate the birthday of Martin Luther King in January, this meant there would be too many holidays, so Washington's and Lincoln's days were combined into "President's day"; and the South finally dropped Lee's birthday.
Actually Lee's birthday is combined with MLK's in some southern states.
Robert E Lee was never president buddy. You lost, give it up.