P.S. Ponyville, Cascade State... Did they name this address before? I don’t remember.
Yes, many times. Ponyville is located in the states of "Cascade State." It's on Twilight's driver's license too and has been seen in the background of things. I was part of a discussion about this with someone else which is why I know, lol. Even if I am newer to this series than some.

I don't know it's earliest existence though.
The quicker example I found was this.
Panel two. Look at the degree hanging on the wall in Cheerilee's office.
EDIT: I am going down a wormhole.
ExampleOh my, I am finding more examples. Panel 3, under the banner that reads "Rain Coast History," it also reads 'Cascade State History.'
Example 2The license plates in panel one read "Cascade State" on them.
Example 3Rarity also has a degree from a University of Cascade State seen in panel 3.
Example 4Example 5 Another license plate on Rarity's car.
Example 6 This might be the earliest example I've found so far from 2019. Twilight's license.
Example 7 Panel 6 has Cascade State on a sign with some cities in the State. Dockland, the city they are located in in this comic appears to be in a different state called Timberland State based on a different comic.
Example 8 Lily's license plate says Cascade State too.
So essentially, Cascade State is the state they live in. Ponyville is a town within the county known as Mare County. Even deeper, Twilight's neighborhood is called, "Woodshire."
Seen here. I hope this helps
@timmelon . Sorry for my essay.