Which Jackson? I always thought it was Jackson, Michigan.

Wikipedia says lyricist Billy Edd Wheeler had no particular Jackson in mind, but many performers insist it was Jackson, Tennessee. Quoting from Wikipedia:

There has been much speculation regarding which city of Jackson the song is about, but Wheeler said: "Actually, I didn’t have a specific Jackson in mind. I just liked the sharp consonant sound, as opposed to soft-sounding words like Nashville." Though Wheeler had no particular Jackson in mind when writing the song, some subsequent singers have specified Jackson, Tennessee.

https://en.wikipedia.org/wiki/Jackson_(song)