[AlotOfReading]

Cities has a particular connotation of dense, urban areas and it's not necessarily the only way high population density can exist on a landscape. California is a good example here, with some of the highest precolumbian population densities in what's now the US. Most of those people lived in Central Valley in large villages often exceeding 2,000-5000 people. However, there was very little high level political organization compared to say, Central Mexico and their primary food sources fall outside typical definitions of agriculture (though they were definitely intensive and involved lots of complicated plant management).

Within the Bay area, populations were centered around exploiting marine resources. Hundreds of large shell middens dozens of feet high littered the precolonial coast, most of which are now destroyed. Even pleasanton, far inland, harvested marine resources because it was a swamp filled with fish.

The PNW still has extant remains of massive precolonial villages, like Ozette [0].

The Southeast/Midwest was another case where we have massive villages, in some cases supporting 10s of thousands of people.

Etc. We don't see these today because we quite literally built on top of them. I used to live near a suburban neighborhood built atop an old Hohokam village where thousands of cremations had been recovered. None of the residents I met knew that the "hill" in the middle was the bulldozed remains of the Pueblo.

[0] https://en.wikipedia.org/wiki/Ozette_Indian_Village_Archeolo...