Iowa ranked 30th in population in the US with an estimated total of 2,936,760 in 2002, an increase of 0.4% since 2000. Between 1990 and 2000, Iowa's population grew from 2,776,755 to 2,926,324, an increase of 5.4%. The population is projected to reach 2,941,000 by 2005 and 3 million by 2025. The population density in 2000 was 52.4 persons per sq mi.

Iowa's population growth was rapid during the early years of settlement. When the first pioneers arrived in the early 19th century, an estimated 8,000 Indians were living within the state's present boundaries. From 1832 to 1840, the number of white settlers increased from fewer than 50 to 43,112. The population had almost doubled to more than 80,000 by the time Iowa became a state in 1846. The great influx of European immigrants who came via other states during the 1840s and 1850s caused the new state's population to soar to 674,913 at the 1860 census. By the end of the next decade, the population had reached nearly 1,200,000; by 1900, it had surpassed 2,200,000. The state's population growth leveled off in the 20th century.

In 2000, the median age in Iowa was 36.6. Just over 25.1% of the populace were under age 18 while 14.9% were age 65 or older, one of the highest concentrations of elderly in all of the states.

In 2002, the largest cities with populations of 100,000 or more were Des Moines, 198,076, and Cedar Rapids, 122,514. Other large cities include Davenport, Sioux City, Waterloo, Dubuque, and Iowa City. In 1999, the Des Moines metropolitan area had 443,496 residents; the Davenport metropolitan area had 358,842 residents that year.