1898 IIRC. Anyone born on the territory of the US is a natural born citizen.
Hell, Barry Goldwater was born in Arizona before it was a state. Nobody even suggested he couldn’t become president. Similarly, children born to American mothers outside the country were always considered natural born citizens.
I assume you are referring to the Wong Kim Ark decision? They didn't declare him a "natural born citizen." They conspicuously left out that verbiage.
They declared him a "citizen" and cited the 14th amendment, which is itself a naturalization act.
Natural born citizens have no need of the 14th amendment.
Similarly, children born to American mothers outside the country were always considered natural born citizens.
No, they were "considered as". If you look at the early acts granting citizenship to people born outside the country, you will notice they never say "is" a "natural born citizen." They say things like "deemed", or "considered as". They never use language that declares them to be a "natural citizen" with certainty.