Notes: 1) The term "immigrants" (or "foreign born") refers to people residing in the United States who were not US citizens at birth. The foreign-born population includes naturalized citizens, lawful permanent residents (LPRs), certain legal nonimmigrants (e.g., persons on student or work visas), those admitted under refugee or asylee status, and persons illegally residing in the United States.
2) In contrast to 1960 to 1990, nonresponse on country or region of birth in both 2000 and 2010 was allocated. For 2000, the "Not reported" category only includes 316 people who were born at sea. For 2010, persons born at the sea were excluded from the total estimate.

Source: US Census Bureau, Decennial Censuses 1960 to 2000 and 2010 American Community Survey.

Also view:

• Region of Birth, 1960 to 2010 (in millions)
• Region of Birth (Numbers and Shares), 1960 to 2010 (an interactive chart)