The USA is the most powerful and highly developed country of the world. It is situated in the central part of the North American continent. Its western coast is washed by the Pacific Ocean and its eastern coast is washed by the Atlantic Ocean and the Gulf of Mexico. The USA is separated from Canada in the north by the 49th parallel and the Great Lakes, and from Mexico in the south by a line following the Rio Grande River and continuing across the highlands to the Pacific Ocean. The total area of the USA is over 9 million square kilometres. The continental part of the USA consists of the highland regions and two lowland regions. The highland regions are the Appalachian mountains in the east and the Cordillera in the west. Between the Cordillera and the Appalachian Montains are the central lowlands which are called the prairie, and the eastern lowlands called the Mississippi valley .The principal rivers of the USA are the Mississippi, the longest river in the world (7,330 km) and the Hudson river. The climate of the USA differs greatly from one part of the country to another. The coldest climate is in the northern part, where there is heavy snow in winter and the temperature may go down to 40 degrees below zero. The south has a subtropical climate, with temperature as high as 49 degrees in summer. The population of the United States of America is about 250 million people, who are called Americans. Most of the people live in towns and the population of the countryside is becoming smaller and smaller.
