Well, it used to be called the Northwest Territory.

Then we expanded even further west and it became the "old west".

Then the "old west" came to mean the Southwest region pre-statehood.

So then they became the "Midwest".

It's probably named by the people who named middle East, like it's the west of the eastern Nations but they named it coz it was in the middle of their way to the east

In my mind, the midwest is west of the Mississippi and through the plains. Colorado starts the traditional west with Texas being the exception.

Read a US history book on the westward expansion and it will all make perfect sense. Hint; it might have something to do with older names remaining in use up until the current day.