Asking what Theodore ‘Teddy’ Roosevelt did is asking a lot, because this beloved president changed the United States in so many ways. For one, he was a Rough Rider during the Spanish-American War. For two, he is pretty much solely responsible for the entire national parks system. For three, he was a progressive who sought to clean up big business and make life safer and better for every American. And all this from a man who wasn’t originally elected–he became president only after William McKinley was assassinated in 1901.