Theodore Roosevelt was the 26th President of the United States.
In the Timeless Universe
Theodore Roosevelt was at the World's Columbian Exposition on May 31, 1893. Garcia Flynn time travels to the night before that date and to that location with Lucy Preston who is held captive. When Wyatt Logan and Rufus Carlin go back in time to try and save Lucy and stop Flynn, they assume Flynn is targeting Roosevelt because he will become president in eight years.
Rufus points Roosevelt out to Wyatt shortly after arriving at the exposition. Rufus comments on how skinny Roosevelt is. Wyatt reminds Rufus that they are looking for Flynn and notices Karl.
Later, Flynn and Lucy discussed his true plans to kill Thomas Edison, Henry Ford, and J. P. Morgan during a meal. During the meal, Karl informs him that Wyatt and Rufus were headed straight for Roosevelt just as Flynn said earlier.
Theodore Roosevelt at Wikipedia