Birthright citizenship goes back at least to the 1840s:
“In Lynch v. Clarke, (1 Sand. Ch. R. 583,) the question was precisely as here, whether a child born in the city of New York of alien parents, during their temporary sojourn there, was a native born citizen or an alien; and the conclusion was, that being born within the dominion and allegiance of the United States, he was a native born citizen, whatever was the situation of the parents at the time of the birth.”
The facts in the case? “The defendant, Julia Lynch, was born in the City of New York in 1819, of alien parents [British subjects domiciled in Ireland], during their temporary sojourn [1815-1819] in that city. She returned with them the same year, to their native country, and always resided there afterwards.”
During their time in the US, the parents regularly expressed the desire to return to Ireland. She was a few months old when they did so, permanently. Yet the case concluded she was a natural born citizen.
See http://tesibria.typepad.com/whats_your_evidence/Lynch_v_Clarke_1844_ocr.pdf for the case.