Alan Gomez, a USA Today reporter, in an Oct. 30, 2018 article, "US Birthright Citizenship Explained: What Is It, How Many People Benefit," available at usatoday.com, stated:

“The principle that anybody born on U.S. soil becomes a U.S. citizen.

It was added to the Constitution in 1868 in the first sentence of the 14th Amendment, which reads: ‘All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.’

The amendment was designed to grant citizenship to freed slaves after the Civil War, overriding the Dred Scott v. Sandford decision by the Supreme Court that had forbidden African-Americans from ever gaining citizenship and the Naturalization Act of 1790 that conferred citizenship only on free white persons ‘of good character.’

In practice, it has become a bedrock of U.S. immigration law that has allowed anybody born in the U.S. to become citizens. Congress also has passed laws extending birthright citizenship to people born in U.S. territories, including Puerto Rico, Guam and the U.S. Virgin Islands.

Citizenship was granted to about 275,000 babies born to undocumented immigrant parents in 2014, representing about 7 percent of all births in the country that year, according to an analysis by the nonpartisan Pew Research Center. Those numbers represented a drop from the peak years of illegal immigration, topped in 2006 when about 370,000 children were born to undocumented immigrants, or 9 percent of all births… 90 percent of undocumented immigrants who give birth in the U.S. arrived in the country more than two years before giving birth.

Those numbers do not include pregnant mothers who obtain visas to travel to the U.S. shortly before giving birth… the total number of babies born through birth tourism [is] about 36,000 a year.”

Oct. 30, 2018