For just shapes the above is a nice visual start.

However a striking feature of the linked article is how frequently there's a major city right near a cell edge.

A more useful list might be constructed by some process involving assigning a "city" an imprint size based on population, and a surrounding 'metro area' based on absorbing any weaker cities that overlap until the process either repeats or is matched by a neighboring city.

A starting point for results that are already similar to that: https://en.wikipedia.org/wiki/Metropolitan_area

The US specific list: https://en.wikipedia.org/wiki/List_of_metropolitan_statistic...

I like that idea of building the regions bottom-up.