The 14th Amendment grants citizenship to all persons born or naturalized in the United States. There are two main forms of citizenship acquisition: jus soli, which is citizenship by birth within a nation's territory, and jus sanguinis, which is citizenship by parentage. Naturalization is the legal process by which a foreign citizen becomes a citizen of another country, and can occur individually or collectively for entire groups. Loss of citizenship can happen through expatriation or denaturalization under certain circumstances. The United States saw its population boom from immigration, growing from 2.5 million in 1776 to 319 million in 2015. While Congress has sole power to regulate immigration, it did not do so for nearly a century after independence