Originally the US expanded quite slowly, due to difficulties in travel and surveying. States were small and communities were close together, about as far apart as a person could walk in a day. At the end of the 1700s, it was only about as big as the blue area in the post above. But in the 1800s, after the Louisiana Purchase, we began to very aggressively expand westward. The construction of the Intercontinental Railroad helped immensely, and towns were being built almost faster than they could name them. The government began giving away land for cheap or sometimes free for anyone who could develop it. Native Americans were forced off their land and onto reservations. State borders became straight lines encompassing vast areas.
That's also very interesting in light of the US superficially appearing to be strongly federal in nature (with the individual states enjoying a great deal of autonomy) - a structure which would historically be known to develop in a bottom-up manner, where preexisting smaller entities would federate to form a larger state.
This history is telling very different story, where those entities were not actually preexisting, but invented by the central authority 😂
The original thirteen colonies worked exactly like that. From then on, it went something like “Hey, federal government, we want to be a state. We’ll follow all your rules, pinky promise.” “Aight.”
It's mostly a shitpost, but the US was originally only the East coast. Over time, the states spread more and more west, so it's saying that all these "new" states are basically a delusion.