United States of America

Note: On January 20, 2009, Barack H. Obama was sworn in as the forty-fourth president of the United States.

Political Status: Independence declared on July 4, 1776; federal republic established under constitution adopted on March 4, 1789.

Area: 3,732,396 sq. mi. (9,666,532 sq. km.); includes gross area (land and water) of the 50 states, excluding Puerto Rico and other territories. These totals are somewhat higher than earlier ones because of a 1990 change in the method of calculating interior waters.

Population: 281,421,906 (2000C); 304,629,000 (2007E). In July 1991 the U.S. government conceded that the 1990 count of 248,709,873 missed about 2 percent of the population but declined to provide an official adjustment for underenumeration. The 2000 figure was advanced by the Census Bureau as being ...