As of July 1, 2007, the estimated population of the 50 states, the District of Columbia, Puerto Rico and the other insular areas of the United States was 305,986,357. Notably, the top nine states in population contain slightly more than half of the total population. The twenty-five lowest-population states contain less than one-sixth of the total population.

The United States Census counts all persons present on the territory of the United States other than short-term visitors, including citizens, non-citizen permanent residents, non-citizen long-term visitors, and illegal aliens. In addition, those serving abroad in the United States Armed Forces and their dependents are also counted in their home state.

Based on data from the decennial census, each state is allocated a proportion of the 435 seats in the United States House of Representatives, though regardless of population, each state is guaranteed a minimum of one seat. The Electoral College is the body that, every four years, elects the President and Vice President of the United States. Each state's representation in the Electoral College is equal to that state's total number of members in both houses of the United States Congress.

By the Twenty-third Amendment to the United States Constitution, the District of Columbia, which lies outside of the jurisdiction of any state, is granted as many votes in the Electoral College as is given the state with the lowest representation in that body. Thus the total representation of the College is 538 members (equal to 100 senators plus 435 representatives, plus 3 members for the District of Columbia). The 11 most populous states have a majority of the electoral college votes, enough to elect the President.