Those who drafted the Citizenship Clause were clear that it would apply in States and Territories alike. Senator Lyman Trumbull, Chairman of the Senate Judiciary Committee during the time the Citizenship Clause was being debated in Congress, explained that the Citizenship Clause “refers to persons everywhere, whether in the States or in the Territories or in the District of Columbia.” During debates over a similar citizenship provision in the 1866 Civil Rights Act, House Judiciary Committee Chairman James F. Wilson expressed the understanding that “Every person born within the United States, its Territories, or districts . . . is a natural-born citizen in the sense of the Constitution, and entitled to all the rights and privileges appertaining to that capacity.”

 It makes sense that the phrase “in the United States” was understood to ensure both States and Territories alike would be included within the geographic scope of the Citizenship Clause. After all, long prior to the ratification of the Fourteenth Amendment Chief Justice John Marshall declared that “the United States” was “the name given to our great republic, which is composed of states and territories.”

More information can be found in Section III.A.2 of Michael Pese’s Motion to Dismiss and also this legal brief filed by prominent citizenship scholars from across the ideological spectrum.