The US Congress, as one of the main governing forces in the US political system, plays a key and unique role. The main task of the Congress is to legislate based on the Constitution, which is extensively discussed in the text of the Constitution. This shows the importance and pivotal role of this institution from the point of view of the drafters of the Constitution. The Congress has a bicameral structure including the Senate and the House of Representatives, and the approval of both houses is necessary to pass laws. Legislation is exclusively in the power of Congress and even the President cannot interfere in this process. Congressional performance is monitored through the confirmation of senior government officials and the impeachment process. In addition to legislation, Congress has other duties; including approving the government budget, approving foreign treaties, approving ministers and judges of the Federal Supreme Court, declaring, war and impeaching the president. This research was done to investigate the position of Congress and the influence and authority of this institution in the policies of the United States of America using a descriptive and analytical method.