About half of the nation’s estimated 11.9 million unauthorized immigrants live in just four states: California, Texas, Florida and New York. Their undocumented populations range in size from about 900,000 to 2.7 million.

In another group of four states—New Jersey, Arizona, Georgia and Illinois—the populations of unauthorized immigrants hover around half a million. The top eight states house more than two-thirds of undocumented immigrants (68%).

However, this does not tell the whole story of the geographic dispersion of the unauthorized immigrant population. In recent years, California’s growth has slowed and a group of fast-growing, new-destination states has attracted many newcomers, both legal and undocumented, from abroad.

California, where 42% of unauthorized immigrants lived in 1990, housed 22% of that population in 2008. A grouping of 28 high-growth states in the mid-Atlantic, Midwest, Mountain and Southeast regions are now home to 32% of the unauthorized immigrant population, more than double their 14% share in 1990.

Five other large states that have been traditional immigrant destinations—Florida, Illinois, New Jersey, New York and Texas—still house 37% of the unauthorized immigrant population, little different from 1990. [See Table B1 and Table B8]

Unauthorized immigrants are 4% of the nation’s population, but states in the West, Southwest and on both coasts have higher shares. In 14 states, 4% or more of the population are unauthorized immigrants. In 21 states, they constitute less than 2% of the population. [See Table B2 and Map A1]

Unauthorized immigrants are 30% of the nation’s foreign-born population of more than 39 million people. In 29 states, they are a higher share of immigrants and in eight of them the unauthorized immigrant population is about half or more of all immigrants. The states where unauthorized immigrants are an above-average share of all immigrants tend to be relatively new immigrant destinations, such as Colorado, Nevada, Georgia and North Carolina. States with low shares either have had many immigrants arriving and staying over the years, such as New York, or still have relatively few, such as West Virginia. [See Map A2]

Metropolitan Residence

A much greater share of unauthorized immigrants than of the U.S.-born population lives in metropolitan areas. Approximately 94% of unauthorized immigrants live in metropolitan areas, compared with about 80% of the U.S.-born population. This difference arises because unauthorized immigrants are more concentrated in principal cities of metropolitan areas (47% live there) than are the U.S. born (29%).