Hi Emilie,
“Polity” is the word I think you’re looking for: a state or a political entity. And those have changed a lot in Mexico over the centuries, as we've all learned!
I use the modern names of the towns/cities and states, and then in the “notes” section, I list the name or names of the encomienda, alcaldia mayor, rancho, hacienda, labor, puesto, real, etc.
This tends to help when working on different platforms.
Saludos,
Manny Diez Hermosillo

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