At issue is the first clause of the 14th Amendment, which states, “All persons born … in the United States, and subject to the jurisdiction thereof, are citizens of the United States.” As the Supreme Court held in the Slaughterhouse Cases shortly after the adoption of that amendment, the main purpose “was to establish the citizenship of the negro,” who, while recently freed in the Civil War, “were still not only not citizens, but were incapable of becoming so by anything short of an amendment to the Constitution.” No one has ever suggested that the three civil rights amendments (13th, 14th and 15th) would have been adopted, absent the need to give citizenship and protection to blacks.
Even more relevant, and totally ignored in the current discussion, is that, while the 14th Amendment reads “all persons born in the United States” are citizens, it has never been disputed that “all” never meant “all.” In 1873, less than five years after the adoption of the 14th Amendment, the Supreme Court addressed the meaning of that citizenship provision by considering the facts surrounding the adoption of the 14th Amendment, “almost too recent to be called history, but which are familiar to us all.” The court concluded, without dissent on this point, that “[t]he phrase, ‘subject to its jurisdiction’ was intended to exclude from its operation children of ministers, consuls, and citizens or subjects of foreign States born within the United States.”
If that had remained the Supreme Court’s ruling on this issue, there would be no need for a new amendment to deny citizenship to children of illegal aliens. But more than a quarter-century later - when the members of the Supreme Court no longer claimed personal knowledge of the events leading up to the 14th Amendment - the court, in United States v. Wong Kim Ark, spoke again on this issue. It first reaffirmed that “all” in the 14th Amendment did not mean “all.” It recognized exclusions: A child born in the United States to a member of an Indian tribe, or to ministers or consul of a foreign government, or to alien enemies in hostile occupation, was not a U.S. citizen. The reason for these exceptions was that such parents did not owe this country “direct and immediate allegiance.”
https://www.washingtontimes.com/news/2010/aug/24/14th-amendment-never-meant-for-illegals/
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All this got distorted in the '60's.