The Census Bureau fully implemented the American Community Survey (ACS) for housing units in 2005 and for group quarters in 2006.
Between 1996 and 2004, the ACS was developed and tested in a selection of counties. Estimates from 2005 to 2010 are available only via the Application Programming Interface (API), Summary File, and FTP site. They are not available on data.census.gov. The ACS provides both handbooks and webinars on both the API and the Summary File for those looking to access data through these tools. The ACS estimates from 2010 to present are available on data.census.gov, as well as the API and Summary File.
Learn more about the program's history in chapter 2 of the Design and Methodology Report.