How To Tell A State Line Is Near

1. There will be a lot of ads for firework stores and/or "adult" stores.

2. The state which you are leaving tries desperately to catch your attention with tons of billboards noting local attractions.

3. The state which you are leaving makes absolutely no attempt to remind you that you were even there.

4. You see billboards for Pure Michigan, as long as you are east of the Mountain Time Zone.  Michigan tourism advertisements are among the most prolific of any region in the United States.  The signs are usually near a state line, hoping to catch long distance travelers. 

5. You will find massive plantings of whatever tree or flower the state is crazy over.  Within a mile of the state line to Florida along any of its entry points will be palm trees planted en masse.  They even make Georgia do it for them on the other side!

6. Out of absolutely nothing you see a line of nearly urban development, complete with high-rise buildings and even rollercoasters. 

I-15 northbound.

This would be Primm, Nevada, which rises almost like a mirage oasis out of the dusty, barren bed of Ivanpah Dry Lake.  The west's lower elevations in general are arid affairs, but this particular part of the Mojave Desert is literally nothing but sand:

It can have water after some heavy spring rains.  I've seen it once, I swear, but yes, that is mostly sand.  A lot of sand.

Yet there Primm arises, the development project of Primm Valley Resorts, complete with multiple gas stations, convenience stores, and three casinos.  Right across the line in the California sun sand would be a gas station with the highest lottery sales for California, just a short walk from the same sort of gas station for Nevada and its lottery.  On the other side of I-15 entering the state from Arizona is the town of Mesquite, which also arises with a heck of a lot of gambling (of superior quality to that found in Primm), albeit from another actual town of Littlefield, Arizona, both Mormon pioneer towns built in the second half of the 19th century alongside the gracious waters of the Virgin River.  Up north, along I-80, West Wendover, Nevada, does yet another developmental surge for the traveler.  Nevada is heavily dependent upon tourism and especially gambling and the state's residents do not hesitate to try to milk you for your worth as soon as legally possible.