I would bet 90% of the properties in the pale green section of the linked map are worth much less than $1M (technically the bar would be $1.25M for a $1M mortgage at 20% down since it would be a jumbo).

In Zillow, choosing recently sold houses only within last 60 days shows mostly $300k to $600k detached single family houses, with a few $1M+ houses in the northeast section (I-90/94 seems to be the demarcation of most $1M+ homes).