At the time of the first federal census, in 1790, the population of the United States was 3,929,214. Between 1800 and 1850, the population almost quadrupled; between 1850 and 1900, it tripled; and between 1900 and 1950, it almost doubled. During the 1960s and 1970s, however, the growth rate slowed steadily, declining from 2.9% annually in 1960 to 2% in 1969 and to less than 1% in the 1980s. The population was estimated at 263,064,000 in mid-1995. The median age of the population increased from 16.7 years in 1820 to 22.9 years in 1900 and to 34.3 years in 1995.
The population of United States in 2003 was estimated by the United Nations at 294,043,000, which placed it as number 3 in population among the 193 nations of the world. In that year approximately 13% of the population was over 65 years of age, with another 21% of the population under 15 years of age. There were 97 males for every 100 females in the country in 2003. According to the UN, the annual population growth rate for 2000–2005 is 1.03%, with the projected population for the year 2015 at 329,669,000. The population density in 2002 was 30 per sq km (77 per sq mi). The major population concentrations are along the northeast Atlantic coast and the southwest Pacific coast. The population is most dense between New York City and Washington, D.C.
It was estimated by the Population Reference Bureau that 77% of the population lived in urban areas in 2001. Suburbs have absorbed most of the shift in population distribution since 1950. The capital city, Washington, D.C., had a population of 3,888,000 in that year. Other major metropolitan areas include the following: New York, 16,626,000; Los Angeles, 13,129,000; Chicago, 6,945,000; Dallas, 3,912,000; Houston, 3,365,000; Philadelphia, 2,607,000; San Diego, 2,983,000; and Phoenix, 2,607,000. Major cities can be found throughout the United States. According to the United Nations, the urban population growth rate for 2000–2005 was 1.0%.