The truth? Abe Lincoln was a conehead.
You read that right - our 16th president was actually the second of three US leaders since America's founding to have alien parentage. Unique to Lincoln's case however was that it was his father Thomas Lincoln who was the alien, which of course caused the conehead gene to pass to ol' Abe and subsequently caused the distinctive cone-bone to develop in his later years as shown in the rare photograph below. To clarify, this picture suggests that all non-conehead pictures of Lincoln taken after 1845 are in fact completely fabricated for political reasons. To keep the need for fakery to a minimum while avoiding political controversy, during his mid 30's when the cone became prominent Lincoln chose to don his trademark cap whenever caught in the public eye (cone-heads were very rare in the 1840's and Lincoln's political campaign felt it best to maintain an image of status-quo).
Ironic that in a nation that was at the time extremely torn over issues of ethnicity, the future president who played a critical role in ending the abhorrent practice of slavery was in fact himself a minority. It's unfortunate to think that if this had been widely known at the time, Lincoln may not have gained the political traction that allowed him to take his stand. However, it is also quite fascinating to realize that the same heritage that could have potentially held him back was very likely a key factor in why Lincoln so staunchly supported equality for all people. Truly he was an American hero.
To confirm, Abraham Lincoln was NOT an alien, and he WAS in fact born in the United States. His father was an alien who was born on the planet Remulak and later moved to Kentucky, Earth, to start a human family.