The 1870 Census found 14,999 people living in the Territory of Idaho. Ten years later, that grew to 32,610 people. In 1890, the year Idaho became a state, it had 88,548 residents. Its population nearly doubled by 1900 and then more than doubled to 325,594 in 1910.
Population grew more slowly in the next 10 years reaching 431,866. Despite the Depression, Idaho’s population rose to 524,873 by 1940. Over the next three decades, Idaho’s population grew an average 14 percent per decade, reaching 667,191 in 1960. Growth slowed to 7 percent in the next decade. The economic prosperity of the 1970s helped Idaho grow an impressive 32 percent, from 712, 567 to 943,935. The double-dip recession of the early 1980s hit Idaho hard, resulting in only 7 percent growth. By 1990, Idaho had more than a million residents. The next two decades brought strong growth — 29 percent to 1,293,953 people in 2000 and 21 percent to 1,567,582 by 2010.
The Census also provides a wealth of historic information for Idaho cities. In 1870, Lewiston’s population was 1,560 — higher than Seattle’s 1,151 at the time. Portland had the Pacific Northwest’s largest population — 8,293. By 1880, Lewiston’s population had fallen to 739, and Boise had a population of 1,899.
In 1890, only 39 percent of Idahoans were female. In those pioneer days, many young men moved to Idaho to work for a few years in forests, farms, sawmills and mines. Over time, Idaho’s gender make-up became balanced. By 1950, women made up 49 percent of Idaho’s population. Since then, they’ve made up half of the population.
The age composition of Idaho’s population has changed significantly over the decades, as family sizes became smaller and longevity increased.Between 1920 and 1970, Idaho’s population grew 65 percent — more slowly than the nation’s population at 92 percent. The fastest-growing region in that 50-year period was southwestern Idaho, which grew 130 percent. South central Idaho grew the slowest at 35 percent. Over the next 40 years, Idaho grew 120 percent — more than twice as fast as the U.S., which was 52 percent. Southwestern Idaho also was the fastest-growing region after 1970, nearly doubling its population by 2010. Northern Idaho and north central Idaho had roughly the same population sizes in 1920 and 1970. Then, northern Idaho experienced a 158 percent growth spurt while north central Idaho grew only 27 percent — more slowly than any other region. Now northern Idaho’s population is more than twice north central Idaho’s population