Established in 1868 with the ratification of the 14th Amendment to the U.S. Constitution, birthright citizenship grants citizenship to all persons born on U.S. soil regardless of the parents' citizenship status. If birthright citizenship is ended, the number of children born without a defined legal status in the United States may reach up to 6.4 million by 2050, according to a new study by Penn State researchers published in the journal Demography.