The U.S. Census Bureau released the first county-to-county migration flow estimates based on the American Community Survey (ACS) in April 2012. It used data collected from 2005 through 2009 that composed the first ACS 5-year dataset. The ACS program combines consecutive yearly datasets to increase the sample size and provide reliable estimates for smaller areas. Even though estimates are produced for 1-year and 3-year datasets, estimates are only published for geographic areas of 65,000 and 20,000 population, respectively. Only the 5-year datasets provide estimates for all counties and county equivalents in the U.S.

The 2006-2010 ACS County-to-County Migration Files included additional files crossed by certain characteristics: age, sex, race and Hispanic or Latino origin. For the 2007-2011 release, the files feature different characteristics: Educational Attainment, and Household and Individual Income (both in 2011 inflation-adjusted dollars). The values for Educational Attainment are for the current residence (i.e., at the time the respondent was surveyed.) The values for the income variables are for the last 12 months prior to being surveyed. Inflation adjustment factors have been applied to the incomes from the responses for the years 2007 through 2010.

Besides county-to-county migration flows, the product package also contains flow data for minor civil divisions (MCD) for a few select states in which they are commonly used as the primary substate aggregate unit instead of counties.

New files for the 2007-2011 have been added that contain the migration flow, migration counterflow, net migration, and gross migration between each county pair or county/mcd pair. These files are only available without characteristics.