It's a story that if it were fiction - it would seem too incredible for the suspension of belief.
A former Texas slave - disguises himself as a successful Mexican businessman - goes to new york city - becomes the toast of the town - hangs out with Teddy Roosevelt - influences U.S. Mexico relations - and is forgotten by the forces of time and history.
But it's a true story - wirtten by Karl Jacoby - the book "The Strange Career of William Ellis: The Texas Slave Who Became a Mexican Millionaire"
