An aerial view of the United States Capitol Building. (Credit: Richard Nowitz/Getty Images)
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Introduction

The legislative branch of the federal government, composed primarily of the U.S. Congress, is responsible for making the country’s laws. The members of the two houses of Congress—the House of Representatives and the Senate—are elected by the citizens of the United States.

At the Constitutional Convention in 1787, the framers of the U.S. Constitution sought to build the foundations of a strong central government. But they also wanted to preserve the liberty of individual citizens, and ensure the government didn’t abuse its power.

To strike this balance, they divided power between three separate branches of government: the legislative, the executive and the judicial.

Article I of the Constitution established the U.S. Congress, a bi-cameral legislative body consisting of two chambers, or houses. As shown by its prime spot at the beginning of the Constitution, the framers initially intended the legislative branch—which they saw as closest to the people—to be the most powerful of the three branches of government.

But as the powers of the presidency and the executive branch expanded during the 19th and 20th centuries, the relative power of Congress diminished, though it still remains essential to the functioning of the nation’s government.

There are 435 total representatives in the House; each state gets a different number of representatives depending on its population. Additional non-voting delegates represent the District of Columbia and the U.S. territories, such as Puerto Rico, Guam and the U.S. Virgin Islands.

Members of the House of Representatives elect their leader, known as the Speaker of the House. The speaker is third in the line of succession to the presidency, after the president and the vice president.

The House of Representatives is considered to be the chamber of Congress that is closest to the people, or most responsive to public needs and opinion. To ensure this responsiveness, people elect their representatives every two years, and all House members are up for reelection at the same time. Representatives may serve an unlimited number of terms in office.

According to Article I, Section 2 of the Constitution, elected representatives must be at least 25 years old, and have been a U.S. citizen for at least seven years. They must also live in the state they represent in Congress.

As the framers designed it, the Senate is more insulated from contact with the electorate than the House, and its members are expected to make decisions based more on experience and wisdom rather than ever-changing public opinion.

In contrast to the House—where representation is proportional to population—each state has two senators, regardless of size. This system of equal representation in the Senate benefits smaller states, as they have a disproportionate influence relative to their size.

Senators serve six-year terms, and there is no limit to how many terms they can serve. Only one-third of the Senate is up for election every two years. According to the Constitution, a prospective senator must be at least 30 years old and have been a U.S. citizen for at least seven years. Like representatives, they must also live in the state they represent.

The vice president is not only second in command of the executive branch, but also president of the Senate. If there is a tie in the Senate when voting on a piece of legislation, the vice president casts the deciding vote. The most senior member of the Senate is known as the president pro tempore, who presides over the Senate in the vice president’s absence.

In addition to the two houses of Congress, the legislative branch includes a number of legislative agencies that support Congress in carrying out its duties. Among these agencies are the Congressional Budget Office, the Copyright Office and the Library of Congress.

Though the Constitution did not mention political parties, they have grown into one of the key institutions of the U.S. government today. Since the mid-19th century, the two dominant parties in the United States have been the Republicans and the Democrats. In both chambers of Congress, there is a majority party and a minority party based on which party holds the most seats.

In addition to the speaker of the House, who is the leader of the majority party, there is also a majority leader and a minority leader. Both majority and minority parties choose representatives to serve as whips, who count votes and mediate between party leadership and regular members of Congress.

Anyone can write a prospective piece of legislation, aka a “bill,” but it must be introduced in the House or Senate by its primary sponsor, either a representative or senator. After a bill is introduced, a small group or committee meets to research it, ask questions and make additions or changes.

The bill then heads to the floor of the House or Senate for debate, where other representatives or senators can propose additional amendments or changes. If a majority votes in favor of the bill, it goes to the other house of Congress to be debated there.

Once both houses of Congress approve the same version of a bill, it goes to the president, who can either sign the bill into law or veto it. If the president vetoes it, the bill bounces back to Congress, which can override the veto with a two-thirds vote of those present in both the House and Senate.

The presidential veto and Congress’ ability to override it are both part of the system of checks and balances established by the Constitution to ensure no single branch of government exercises too much power.

In addition to writing and passing laws, Congress also has various other powers, including the power to declare war. Congress also creates an annual budget for the government, levies taxes on citizens to pay for the budget and is responsible for making sure money collected through taxes is used for its intended purpose.

Though the two chambers of Congress must jointly decide on how to exercise many of the powers given to them by the Constitution, each chamber also has specific powers that only it can execute. Among the unique powers of the House of Representatives are impeaching a federal official and proposing all tax legislation.

For its part, the Senate alone can ratify treaties signed with other countries, try impeached officials and confirm all presidential appointments, including the members of the president’s Cabinet and justices of the Supreme Court.

The Legislative Branch, WhiteHouse.gov.
Legislative Branch, USA.gov.