The Federal Bureau of Investigation defines Its mission in clear terms: to protect and defend the United States against terrorist and foreign intelligence threats, to uphold and enforce the criminal laws of the United States, and to provide leadership and criminal justice services to federal, state, municipal, and international agencies and partners.

One of the world's most powerful and secretive intelligence services, the Central Intelligence Agency (CIA) serves a critical role in the shaping of American policies by providing foreign Intelligence related to national security issues to the U.S. president and senior U.S. policy makers. The process of gathering and analyzing intelligence involves spies and satellites, foreign agents, and researchers working at the CIA's headquarters.

A history of the cases that have been presented before the U.S. Supreme Court offers a nearly comprehensive account of the issues that have shaped American history. By protecting the spirit of the Constitution and interpreting it when necessary, the Court's mission is to offer all Americans the opportunity for justice.

For more than two centuries, a president's term in office has begun with an inauguration and the oath of office. But within that simple vow to "preserve, protect, and defend the Constitution of the United States," an extraordinary range of power and responsibility is placed on each new president.

For more than 200 years, the House of Representatives has stood as the keeper of American democracy. Over the years, the House has been a center stage for controversy, scandals, and tremendous legislative victories.

In the wake of September 11, 2001, the U.S. government felt the need to establish a special department to handle national security--the Department of Homeland Security. But the idea of national security is not a recent concept, and terrorism is not a new concern. In truth, every generation of Americans has experienced some worry that they might be attacked in their homes.

The story of the United States Senate is more than the description of the powers assigned to the upper house of Congress. These powers are considerable, including the making of laws to govern the United States in partnership with the House of Representatives, and the unique authority to provide advice and consent to the president of the United States.

In March 1854, a group of men gathered to form a political party that reflected their concerns about life in America. They were opposed to the spread of slavery, supported high taxes on imported goods, and were in favor of homesteading to help settle the rapidly expanding Western territories. Since then, the Republican Party--like the American political system--has undergone many profound changes.

The election of a president is one of the most important events in American politics. While the concept is the same, the process of electing presidents has changed considerably since George Washington became the first president of the United States: political parties now play a key role in the election process, campaigns dramatically affect voters' impressions of the candidates, and the rise of television and the Internet has greatly increased the information available to voters.

Democrat or Republican? These two parties have become fixtures in the American political experience--the main choices in all elections, from the national to the local level. But the distinction was not always so clear. When the Democratic Party was first established by Thomas Jefferson, it was actually known as the Republican Party. Today it is the oldest political party in the United States, and among the oldest political parties in the world.