Why was Theodore Roosevelt called the "American Giant" and what did it mean?

Theodore Roosevelt was called the American Giant because he was the first to do many things. He created a new set go standards for anyone who had the slightest desire to be a decent human being. He did it with the weight of the country on his shoulders. Roosevelt was a capable of doing amazing things, and he knew it. He applied himself to everything he did, and came head on at everything he believed in. Because of this, he is considered to be one of the best president.

He led the 1st US Volunteer Cavalry called the Rough Riders