The majority of illegal immigrants in the U.S. live in 20 metropolitan areas, with a substantial number in sanctuary or immigrant-friendly cities, according to a study released Thursday by the independent Pew Research Center.

In 2014, the 20 metropolitan areas with the largest undocumented population were home to 6.8 million, or 61%, of the estimated 11.1 million in the country. In contrast, only 36% of the total U.S. population resided in those metropolitan areas.

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