Something that surprised me in my travels (which are primarily West of the Mississippi) is how often the states actually line up with a significant geographic shift. Arizona is endless orange desert. New Mexico immediately becomes rainbow painted cliffs. Utah is somehow entirely vertical. California is a contradiction of green desert. Nevada is like a chemical mine puked on a bunch of bumpy ridges. Northern New Mexico falls off a cliff and the bottom is Texas.

If you watch closely, usually something fairly dramatic happens in the landscape within a few miles of the border.

Roads. It is pretty common around where I grew up to notice you are in a different states when there is a sudden shift in road conditions. They never communicated about when to do repairs or anything, so it was almost always an obvious line between either a really shit road and a smooth one, or vice versa. Sometimes you could even tell based on the noise or feel of the road, if the other state uses different road construction materials.

I can tell when I'm driving from NY into CT when suddenly there's traffic for no reason and everybody is driving like an asshat.

My crossing is a river, so basically pretty obvious. I was out of town on a work trip though and I was warned that when I was going to a Home Depot to not miss the turn because I would be at the Canada border and doing a U-turn there would probably get me chased down and pulled over.

Canadian here, never crossed into the U.S nor seen the border but at some point in time I drove down 0 Avenue and saw a house with an American flag and my instinct was “That’s the wrong country chief” but I was far wrong.

Really put into perspective how “secure” our borders are.

Between States with more or less lax laws on liquor, firearms, explosives, tobacco, etc, there's usually various merchants immediately on the side of the border with more lax laws.

It's usually on a highway and highways usually have a "Welcome to …" sign at the border.

Yeah, the roads instantly change color and texture. If you cross into south carolina, BAM. All the roads are whiter and rougher.

I can sometimes tell what county (not country) I am in from differences in the design of street signs (mostly the street name signs at stop lights), changes to the look of highway overpasses, and whether or not Flock cameras outnumber people.

There are 50 states and a lot of different border arrangements. If a border is something dramatic like a river and you know that's the state border you can tell.

Often the only way to tell is a change in road surface or signage, or the "Welcome to state" sign. Google navigation will tell you too.

Because they go through the door in the border wall to Mexico.

The roads go to absolute shit crossing from Ohio into Indiana. And it's not like we have exactly great roads here...

I live on a border and my jogging path cuts through one state and then rounds back home to the other. The only way you can tell a difference is the states have different paving and road work schedules, so usually one state has more shitty roads then the other.

field on one side, field on the other. if I am on the interstate, the surface gets really shitty on our side because brownback and the republicans in topeka drained the highway fund to give the koch bros and fat corpo-farmers a tax break.

Heading west out of Connecticut into New York the most obvious difference is they don't trim tree branches over the road/power lines. It suddenly feels like you're driving through a tunnel of green. Its actually quite nice but those parts of nys must have a lot of outages after storms.

I pay money to cross a large river.

My state has piss poor roads.

Every time I leave my state the roads are noticeably smoother and less noisy.

It’s very distinct and almost comical.

It usually depends on how big the road is that you're driving on. Most state borders are in very extremely rural areas, so sometimes there's not even a sign. On interstate highways it's always quite obvious, but little country roads might not have any signage at all.

• There's usually no obvious change in architecture, no; often the only architecture is farm buildings, and those are more or less consistent architecturally. And broadly speaking architecture is regional, rather than state-specific; the difference in architecture from northern Indiana to southern Indiana is far more pronounced than the difference in architecture from southern Indiana to northern Kentucky, for instance.

• As noted elsewhere, sometimes the infrastructure can be different (usually seen in road quality), but most states tend to number their county roads in different ways, so when you cross the border you'll often find that the number of the roads you're crossing tend to suddenly shift from "300W" to "2300E." The signage may also change very slightly, though if you're truly out in the middle of nowhere, there might not be any signage to change.

• Agriculture, like architecture, is usually much more defined by region than by state. All of the states around mine farm corn, wheat, and soybeans, just like mine does. Most also farm cows, though Kentucky notably has a lot more horses than any of its neighbors, so that can be a tell. But you don't get into a ton of ranching until you get further west, and then you see large changes across multiple states at a time.

• Store brands often do change, but again, since most crossings are in rural areas, there often aren't any stores around to notice the change right away. You'll roll out of a state with a lot of Meijer stores and into a state where Publix is the regional grocery store, but until you get into a town, there's no way to know.

• Culture is probably the thing you'll notice least. People who live in rural areas tend to think of themselves as American before any other identifier, so you'll find a lot of jingoism anywhere on both sides of any border. American flags, Christian crosses, gigantic emotional support pickup trucks, bizarrely aggressive patriotic bumper stickers, Trump signs and flags, etc. Depending on where you are those sorts of things are accompanied by very clear signs of deep poverty (mobile homes, trash-strewn lawns, run-down houses), but they can just as often be on or around very well-kept houses on huge acreage.

• And if you mean "culture" in the sense of theater, music, etc., you're unlikely to find any at all near a state border.

I guess the other thing is that Google Maps will tell you "Welcome to (state)" when you're navigating. There are some times that that's the only way you'll know.

I'll never forget driving home from college with some friends for the holidays one year. I was from PA, he was from Ohio and had never been more east. We were headed to NY with another friend and our route took us briefly through Jersey.

"How will we know we're there?" he asked as the car suddenly lurched and felt like we hit a gravel road despite ostensibly being a paved highway ...

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

Connecticut is making a bold claim here to anyone leaving NY

you know, most roads will tell you. The change in asphalt for sure will tell you exactly

plus for me at least, Idaho is different than Washington

the roadside advertisements is instantly different

the highways are laid out in much different ways

the people are absolutely different almost to an extreme

When you pass into Indiana, you're immediately overcome with this opressive sense of forboding and despair. Also the roads immediately turn to shit.

Leaving South Carolina to enter North Carolina or Georgia, the roads are so much better and there’s a noticeable decrease in overall loudness in road noise.

There is a body of water under the bridge, toll collection booths right before or right after the bridge crossing. Also GPS confirms it.