The U.S. Census American Community Survey (ACS) is the source for detailed demographic data at the national, state, and local levels. The ACS was provides more timely demographic, social, economic, and housing data than the decennial census.
The ACS provides one-year estimates for geographic areas with populations of 65,000 or more. Three-year estimates are available for geographies with populations of 20,000 or more. Five-year estimates are reported for areas with populations less than 20,000. ACS estimates are updated for all geographic areas annually.
It is important to remember that the ACS is nationwide survey and a sample, not a the national census. Because the data is collected continuously (about 250,000 surveys each month) the results describe the characteristics of a population over time, rather than provide a count of the population at a specific point in time like the decennial census.
ACS data is also available through FactFinder.