databases of statistical information
U.S. Department of Homeland Security
The main U.S. government source of statisticial data on immigration
U.S. Census Bureau
The U.S. Census Bureau site with data on immigration to and emigration from the United States.
Migration Policy Institute
The Migration Policy Institute provides access to their statistics, facts and maps on migratio and immigration in the U.S. and abroad, with databases that are searchable by state.