Based on the map above the American West in 1789 would be Kentucky, Tennessee, Mississippi and Alabama. Those states were not named in the map but as comparison with the next map would show those four states were the wild west of 1789. A Kentucky born and bred said “Kentucky was the beginning of the west”.
In 1845-1846 America expanded making Texas, Arkansas, Missouri and Louisiana the new West. This was the era we see in the movies where cowboys and outlaws start their trail from Indiana, Kentucky, Tennessee and Mississippi, shoot at each other then run off to Mexico via Texas to avoid the Sheriff.
The California Gold Rush (1848–1855) pushed American west farther. By 1884 to 1889 the America we now know has shaped up to make Oregon, California and Nevada as the West. Texas and Florida and Louisiana became south.
In 1890 Americans gave up the horseback and arrived in the West by automobile. Later representatives from all the western states built the Cowboy Hall of Fame and Western Heritage Center to showcase western culture.
When a new immigrant Filipina was asked where is America's Midwest she said "The west is in the West Coast, the east is in the East Coast. The Midwest is everything in between."