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. Today, the United States of America is the lone super power in the world. The United States is very strong. Power, however, is not the only thing that comes with being a world leader. As a world leader, America also has a lot of responsibility to the rest of the world. In the twentieth century, the United States struggled to balance its power with its responsibility in new ways.

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.

By the beginning of the 1800s, America was a young country led by people who were ready to fight to defend American rights on the seas and at home. They were eager to teach Europe's older nations a lesson, and they wanted to add to America's land. America fought the War of 1812 as well as a war in Florida. The US came out of these wars stronger than ever— and the people of the United States were ready for America to grow still bigger.

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. In the 1830s, over fifty years after the United States had won its independence from Britain, Americans were still delighted with their young country. That sense of hope and freedom are still a part of the United States today. As you learn about the settlers who rode the Oregon Trail to new land in the West, you will gain a better understanding of how America became America

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. People like Thomas Paine, George Washington, James Madison, and Thomas Jefferson built the foundation of values and ideals on which America still stands. Learning about America's birth will help you understand the country it is today.

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. Thomas Jefferson was one of the most important of these thinkers. During his presidency, the Louisiana Purchase doubled the geographic size of the United States. And perhaps most important, Jefferson helped define what is best about America.