All states, even small ones like NH have regions that inhabitants use to subdivide the place. A few are familiar names to outsiders – Cape Cod, Black Hills, Long Island, Outer Banks; many more are immediately understandable once one has heard it. If you hear that a state has a mountain region or mountain district as a distinct idea known to natives, it’s fairly simple to pick up a map and figure out where that is. The names vary slightly and are not quite predictable, but neither are they surprising. It’s Connecticut Coast, not Seacoast. Some say Maine Coast, others say Coastal Maine, but no one says Maine Shore. New Hampshire’s region next to the Atlantic is The Seacoast. Massachusetts breaks that up into distinct bits.
Instate, an important area might own the geographic feature: The Lake*, The Beach, The Island, The River. Outsiders get annoyed at the provincialism of this, but language is about communication. Others are obvious enough to be predictable even if previously unknown. I’ll bet they call that The Panhandle in Oklahoma. (They do.)
Others are less obvious, and those are more fun. Anyone could figure out what the Lakes Region or White Mountains refer to, but you have to pause a bit for others. We used to have the Golden Triangle in NH, but I haven’t heard the phrase in years. Above The Notch is a real thing here. Some are not fully distinct even to natives. Upper Valley refers to the area around Hanover and Lebanon, sometimes including parts of Vermont, sometimes not. But Upper Connecticut Valley might mean that area, or the one farther up near Colebrook. The Merrimack Valley in some contexts means everything from Nashua to Franklin, but since the high school of that name went in it more likely refers to the upper half of it.
I know Vermont’s Northeast Kingdom, and a few Massachusetts regions, but I’m interested in the regions of your states that tend to be known internally, but don’t occur to outsiders.
*There are nuances here. The speaker’s family may own property on another lake, or those in the conversation may know that some other lake is meant. Yet if they move to a different conversation at the same function they might revert to The Lake meaning Lake Michigan, and none other.