U.S. Constitution: Article I, Section 2
Article I, Section 2 of the U.S. Constitution sets the ground rules for the U.S. census. It states that seats in the House of Representatives shall be divided among the states by population based on a census conducted every 10 years. U.S. Constitution, Article I, Section 2 states in relevant part:
Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Person.
The actual Enumeration shall be made with three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct.
The Number of Representatives shall not exceed one for every thirty Thousand, but each State shall have at least one Representative;...
As you can see, the Constitution states very clearly that a census shall be conducted every 10 years. It also states, from the first quoted line above, that "Representatives and direct Taxes shall be apportioned among the several States…" So, the census does two main things: (1) determines the proper number of representatives in each state, and (2) how to direct taxes. However, the language fails to state a number of things, including how many total Representatives Congress may have.
Because the Constitution fails to state how many total representatives Congress may have, Congress regularly increased the size of the House in the early years of the country to account for population growth. Then, in 1911, Congress fixed the number of House members to 435 in order to keep the House from becoming too big.
The Constitution also fails to state how to conduct the census. It merely says "in such Manner as they shall by Law direct." In the early days of the United States, canvassers – people who conduct the census - traveled by foot and horseback to collect information. Today, the United States Census Bureau under the United States Department of Commerce conducts censuses with sophisticated equipment such as Global Positioning System (GPS) devices to better assist canvassers. (GPS devices are navigational systems involving satellites and computers that can determine the latitude and longitude of a location.)
Next, we’ll go over what you’ll need for the 2010 U.S. census.