Check out a dusty new chalkboard map of demographic doubling and halving...
Note, this census question is electively chosen by census respondents and individuals' preferences of identity may change, as well as the subtly shifting terms of the survey itself.
So take these maps with the caveat that some places can have already very low populations so doubling or halving can potentially happen quite easily -though in the context of the set of groups this issue actually provides an interesting dimension of comparison.
This map has been updated to correct for a miscalculation of doubled American Indian/Alaska Native counties in a previous version. The update has revealed different, and more, counties where that population has doubled.