As the Supreme Court pointed out in Minor (1875):
"Additions might always be made to the citizenship of the United States in two ways: first, by birth, and second, by naturalization. This is apparent from the Constitution itself, for it provides that "no person except a natural-born citizen, or a citizen of the United States at the time of the adoption of the Constitution, shall be eligible to the office of President," and that Congress shall have power "to establish a uniform rule of naturalization." Thus new citizens may be born or they may be created by naturalization."
Are there any “native-born”, “foreign-born”, or “aliens” on that list???
http://www.foreignborn.com/visas_imm/start_here/4birth_abroad.htm
Actually there was a third: by marriage.