At 3.79 million sq mi (9.83 million sq km) and with around 320 million people, the United States is the third-or fourth-largest country by total area and the third-largest by both land area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the U.S. is also extremely diverse, with deserts, plains, forests, and mountains that are also home to a wide variety of wildlife.