A 2011 survey by the U.S. Census Bureau found 40.4 million foreign-born people living in the United States, making up 13 percent of the total population. Foreign-born refers to people who were not U.S. citizens at birth or who were born outside the United States, Puerto Rico, or other U.S. territories and whose parents are not U.S. citizens. This includes both authorized and unauthorized immigrants. The foreign-born as a percentage of the total U.S. population is lower than historical highs of slightly less than 15 percent between 1890 and 1920.
Source: Pew Research Center