<P> As of April 1, 2010, the date of the 2010 United States Census, the nine most populous U.S. states contain slightly more than half of the total population . The 25 least populous states contain less than one - sixth of the total population . California, the most populous state, contains more people than the 21 least populous states combined, and Wyoming is the least populous state, with a population less than the 31 most populous U.S. cities . </P> <P> The United States Census counts total persons residing in the United States including citizens, non-citizen permanent residents, and non-citizen long - term visitors . Civilian and military federal employees serving abroad and their dependents are counted in their home state . </P>

Largest state in the united states by population