The United States Senate is part of the United States Congress, which is a small group of elected people who decide the laws of the country. Every U.S. state elects two people to represent them in the US Senate. These people are called senators. Since there are 50 US states, there are 100 senators. Senators only serve six years at a time, and one-third of them are picked every two years. Originally the legislature of each state decided who their senators would be. After 1913, all the people of the state chose their senators by vote. The Vice President of the United States is in charge of the Senate, but only does anything when there is a tie vote or a special event.