The United States has seen declines in intra- and inter-state migration since the 1980s, a long-term decline that cannot be explained by short-term period effects such as economic recessions. The chapter begins by reviewing the chief data sources that are available to research internal migration in the USA. It then considers explanations that have been offered for the US migration decline. After econometric modelling, it argues that the migration decline is a consequence of four fundamental shifts in American society. First, there has been a decline in migration in order to gain economic opportunity. The cohort effects documented suggest that migration has declined because large older age cohorts such as the ‘baby boomers’ have crowded out opportunities for younger age cohorts. Second, while ICTs are associated with an increase in geographic mobility, the opposite may be true sometimes: ICTs can be associated with a reduction in geographic mobility. Third, since ICTs offer alternatives to migration, they provide a means for avoiding risks associated with migration during economic uncertainty. Fourth, migration may be hindered by the increasing regulation of state housing and labour markets. It is apparent that the USA is now becoming a more ‘rooted’ society.