Which states (and/or DC) are in the Midwest?

[muon2]

I think that the Midwest has two parts: the Great Lakes and the Great Plains with the Mississippi as the natural divide between them. Both parts are agricultural, but the Great Lakes has more reliance on heavy industry and the Ohio river is the natural southern boundary. The states of the Great Plains have states that overlap other regions, so I look to the areas of the most population in a state. I find that Omaha, KC and OKC are all easily classified as Great Plains cities. Southern MO and SE OK are more southern, but the main population is in the Plains. The Black Hills and Badlands can put the western Dakotas in the West, but again the main population is in the center and east.

[muon2]

There are the givens (MN, WI, IA, IL, IN, MI, OH) and there is Missouri which I consider belonging both to the Midwest and the South.  

Neither the St Louis metro (1.897 M in MO in 2010) nor the Kansas City metro (1.085 M in MO) are southern cities. Together they make up half of state's population (49.8% in 2010). Add in the northern rural areas and it's more than half. The southern region of MO is probably no more than a third.

Lots of states have part of their population in a different region. If one must place a state it seems most reasonable to place it in the region where the majority of its population resides.

[muon2]

I take it there is no category for "border states." I might put MO, KY and WV in that category. And is Oklahoma a plains state or a southern state?

Hence my suggestion that a state be placed based on the region where a majority of the population resides. MO and OK are midwestern (if as I think it includes the plains) , KY is southern. WV is tough since it has significant populations in the Appalachian Northeast, the Appalachian South, and some of the Midwest along the Ohio valley. Since the more of the population matches with western and central PA, than with western VA and eastern KY, I put it in the Northeast since PA is there. TX has the same problem of a split between three regions.