Public debate over the propriety, merit and feasibility of the Census Bureau asking questions about religion has waxed and waned over many decades with religious groups, civil liberty groups, social scientists and the Census Bureau's own staff divided over the issue.
The U.S. Census Bureau has not asked questions about religion since the 1950s, but the federal government did gather some information about religion for about a century before that. Starting in 1850, census takers began asking a few questions about religious organizations as part of the decennial census that collected demographic and social statistics from the general population as well as economic data from business establishments. Federal marshals and assistant marshals, who acted as census takers until after the Civil War, collected information from members of the clergy and other religious leaders on the number of houses of worship in the U.S. and their respective denominations, seating capacities and property values.
In 1880, census takers started collecting more in-depth information from religious leaders on topics ranging from average worship attendance to church income, expenditures and debt. The scope of inquiry about religion was expanded again in 1890, when census takers gathered information about the number of ministers in each denomination.
Read the full report A Brief History of Religion and the U.S. Census on the Pew Forum on Religion & Public Life's Web site.