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. But some things have not changed. The basic framework of the American nation was laid out by the Founding Fathers in the Declaration of Independence, the Constitution, and the Bill of Rights. Over the years, these have remained basically the same. The U.S. economic system has grown—but it too is much the same. So is America's system of voting and elections. As you learn about how these important parts of the United States work in the twenty-first century, you will come to better understand what makes America the nation that it is.