Crossing into Wisconsin from Minnesota, I will start seeing lots of fireworks stores.

There’s a spot near me where 3 intersect right on the road. The pavement is in a different state of disrepair for each. You can see it and hear it driving along.

this is such an adorable question.

Crossing into Wyoming from Utah is hilarious for this. Suddenly there's porn, cigarettes, beer, fireworks, and more porn!

I once lived in a small city right on that state's border. It was sort of a suburb tho to a very large city in the neighboring state. The major roads would have signage, but on the smaller roads there really wasn't any way to tell. The main difference tho was that the large city's public transit options extended pretty far out even into the small towns along the border, but wouldn't at all come into my small city..

Where I live now, you have to cross a very large river to get into the neighboring state. What's worth sharing here tho, is that there is a nearby county line, where even tho there's a sign, you don't need it at all. The landscape/biome changes pretty much at the county line.
It goes from a sort of temperate rainforest-like climate, to arid grassland/high desert climate. You'll be driving thru areas with large, old growth evergreens and lots of ferns underneath, and then it turns to dead, dry, brown grass and sagebrush shrubs everywhere. Like, it could also even be raining the whole first part of the drive there, but once you get to this county line the rain almost always dissipates. It's pretty wild.

My state disallows billboard advertising, which I forget until I cross into another state and have to suffer through Jesus and injury lawyer ads.

My southern neighbor:

Been a few years since I lived in Minnesota, do you still see signs for Spotted Cow beer as you cross into WI? I had friends bringing trunks of sixers back and while I would always accept a free craft beer, I didn't understand the hubbub.

When I lived in the Midwest one of the clearest signals (aside from the obvious signage) was the college football team swag on cars and in front of houses.

Ah yes, the Garden State. What do they garden? Apparently strip malls and trash.

I never noticed them! I don't tend to pay attention to adverts though.

Delaware makes you pay to leave New Jersey

I still like to imagine fighter jets or attack helicopters swooping in to blow up speeders, or in more modern times drone strikes

michigan?

I plead the 5th.

It’s illegal to own one in Virginia. If you’re from another state where they are legal you’re supposed to take it off your windshield or at the very least turn it off if you have a more built-in kind. I remember they used to be relatively common in the ’90s and early ’00s but I really don’t see them very often anymore, so I don’t know if that’s as much of an issue nowadays.

I feel that too, and i live here

The limited distribution makes people think it's a mind-blowing beer. It's pretty good.

I pray for my suspension every time I go from Ontario to Quebec.

I travel a lot throughout the US, and sometimes the changes are obvious while other times I can be driving and not entirely sure which state I'm in just from looking around on the highway. As others have said while driving on a major highway a clue can be a huge store full of items like fireworks just across the border from a state they aren't legal in.

The geography and environment can certainly be a big clue. Driving through West Virginia there are tunnels through large mountains, Pennsylvania around the Pittsburgh area has steel bridges, Louisiana has highways raised up from the muck, there are mountains that the highways wind around in North Carolina that give way to pretty flat highways as you go south. Kentucky has long depressing stretches of straight boring road. I've noticed even traffic patterns can say things as Georgia highways always have a higher number of semitrucks than anywhere else for example. Nevada is flat and open but as you go into Utah it gets windy and rocky, and cell signal usually goes out for a bit.

Staying in different states I notice alcohol sales rules are different. In some states you basically don't see any alcohol outside of designated stores for it including no beer at gas stations, in other states you see beer for sale widely but hard liquor only at designated stores, and in other states hard liquor at WalMart is perfectly normal.

I've found on the whole that people are actually nicer than average in Utah. While coffee shops exist I have noticed in offices there is often a lack of a central coffee machine.

Louisiana everyone I deal with from there has a tendency to be much more relaxed than average about showing up exactly on time for things. Louisiana itself also has a cultural divide between the northern part which is more generic US south, and the southern part which has the more creole and tourist heavy atmosphere.

I honestly don't mind Ohio. I know it's an internet meme to hate it, but aside from their obsession with dumping chili on unrelated foods it's decent. Has a strong blue collar streak kind of like Pennsylvania culture.

Texas has a big cowboy influence and they don't let you not know it. The roads tend to big big and wide which is great, except the freeways especially in Dallas can become confusing multilevel nightmares.

California has lots of Spanish signs, lots of first generation Mexicans who bring culture with them. Lots of for example Mexican super markets. Californians have a culture of going FAST on freeways if there isn't gridlock traffic, in some cases going 100mph just barely keeps you up with traffic.