How Big Was America? US Population in 1900, 1945, 1990, and Today

Pick four years and you can watch a country turn into a different country. In 1900 the United States counted 76,212,168 people. Today the Census Bureau's latest estimate puts it at 334,922,499. That's more than fourfold growth inside a span that some families have lived across in three or four generations. The raw totals are easy to recite. What they mark is harder, and more interesting, because each milestone sits on top of a specific set of forces.

1900: 76 million and still mostly rural

The 1900 census recorded 76,212,168 people. Put that next to the very first census in 1790, which found 3,929,214, and the nineteenth century reads as one long expansion: westward settlement, high birth rates, and wave after wave of European immigration feeding into a country that was still largely farms and small towns.

By 1900 the industrial cities were pulling people in, but the center of gravity was rural. The population was young, fertility was high, and the immigration door was open wide. A 76 million-person nation in 1900 was already the most populous country in the developed West, and it was about to grow faster than almost anyone living in it expected. If you want the long arc behind that number, the full timeline from 1790 to today lays out every decade in order.

1945: about 140 million, and not a census year

This one needs an asterisk. The decennial census runs on years ending in zero, so there is no 1945 count. The figure of about 139,928,000 is a U.S. Census Bureau intercensal estimate, the Bureau's reconstruction of where the population sat between the 1940 and 1950 counts. Treat it as an estimate, not a headcount.

Even with that caveat, the number tells the story of the half-century. From 76 million in 1900 to roughly 140 million in 1945, the country nearly doubled. Two things drove it. Immigration ran heavy through the early decades before restrictive 1920s laws slowed it. And the population kept reproducing faster than it died, even through a world war, a flu pandemic, and the Great Depression. By 1945 the war was ending and the demographic event that would define the next two decades had not yet shown up in the totals. It was about to.

1950: 151 million and the boom begins

The 1950 census counted 151,325,798. The jump from the 1945 estimate is the leading edge of the baby boom, the postwar surge in births that ran from the late 1940s into the early 1960s. Returning servicemen, cheap housing, suburban expansion, and a confident economy turned the birth rate up sharply. The country that had nearly doubled between 1900 and 1945 was now adding people at a pace it had not seen in decades, and this time it was doing it through births at home rather than arrivals from abroad.

That cohort, the boomers, becomes the single most important variable in American demographics for the rest of the century. Everything from school construction in the 1950s to the aging of the workforce now traces back to it.

1990: 249 million and a maturing nation

By the 1990 census the United States held 248,709,873 people. The boom was long over. Fertility had settled well below its midcentury peak, and the engine of growth was shifting. Immigration, reopened and reshaped by the 1965 reforms, was again becoming a major contributor, now drawing more heavily from Latin America and Asia than from Europe.

A 249 million-person country in 1990 was older, more urban, and more diverse than the one of 1950. It was also growing more slowly in percentage terms, which is what happens as a population matures: the share of people in their prime childbearing years shrinks relative to the whole, and total growth leans more on migration and on people simply living longer.

2000 to 2020: the climb past 300 million

The pattern held into the new century. The 2000 census reported 281,421,906. By 2010 the count was 308,745,538, and the country had crossed 300 million somewhere in between. The 2020 census put the total at 331,449,281. Across those two decades the United States kept adding tens of millions, but the rate of increase kept easing, with immigration carrying more of the load as births slowed.

Today: 335 million and unusually slow growth

The Bureau's most recent estimate is 334,922,499. The notable thing is not the number, it's the pace. Growth between 2020 and today has been unusually slow by the standards of any of the milestones above. Birth rates have stayed low, the population is aging as the boomers move into their seventies and eighties, and the swings in immigration and the mortality shock of recent years all show up in the flattened curve.

Look across the four checkpoints and the formula changes from one era to the next. Nineteenth-century growth ran on births and European immigration. The 1900-to-1945 doubling ran on the same fuel with the door narrowing. The postwar surge ran on the boom. The decades since have run increasingly on immigration and longevity rather than family size. What's slowing now is the part the boom used to supply. For where this trajectory points, see our look at what the U.S. population will be in 2050.

If you want to put these milestones to work, the national page keeps the current totals and trends in one place, and the compare tool lets you set states and decades side by side to see where the growth actually landed. You can also watch it move geographically on the map. The country in these four snapshots is the same place four times over, and the numbers are how you tell the difference.

Sources

Figures are from the U.S. Census Bureau: the Bureau's history pages, the decennial census for years ending in zero, and the population estimates program for intercensal and current-year figures, including the 1945 estimate and the latest national total.