looking at past election results

[old timey villain]

I'd say 1992 for CA, WA, OR, NV, CO, NY, NJ, PA, NH, ME, MD, DE, FL, IL, MI, WI, NM

1992 was a very big year since all those states have been solid blue or swing in nearly every election since then.

[old timey villain]

For Kentucky it's 2000 when the urban/rural split took hold.

The era from 1994-2000 was really sort of a realignment nationwide. The whole country swung right in 1994. The urban areas recovered. The rural areas didn't.

I believe I'm too young to even remember a time when Democrats were undeniably strong in rural areas.