The United States' boundaries have expanded over the centuries—and at the same time, Americans' ideas about their country have grown as well. The nation the world knows today was shaped by centuries of thinkers and events. Teddy Roosevelt's America, for example, was a different one from today's version, and yet Roosevelt's ideas and actions shaped present-day America. The actions and policies of Presidents Roosevelt, Taft, and Wilson also led to America's involvement in the Caribbean and in Central America. As the world headed toward World War I, the United States was ready to take its place as a leader on the global stage.