The census is an essential part of American democracy. The United States counts its population every ten years to determine how many seats each state should have in Congress. Census data have also been used to levy taxes and distribute funds, estimate the country’s military strength, assess needs for social programs, measure population density, conduct statistical analysis of longitudinal trends, and make business planning decisions.

We looked at every question on every census from 1790 to 2020. The questions—over 600 in total—tell us a lot about the country’s priorities, norms, and biases in each decade. They depict an evolving country: a modernizing economy, a diversifying population, an imperfect but expanding set of civil and human rights, and a growing list of armed conflicts in its memory.