The Great Frontier is the title of a classic 1952 book by Walter Prescott Webb, in which he writes of the effect of frontier on the Europeans who moved to North America.
That frontier, they found, was incredibly rich, and populated by about one million hunter-gatherer Indians, who were busy bashing out the brains of the babies of other tribes and not much else. Growing a little corn, perhaps.
The frontier changed the mentality of those who encountered it.
I was raised near the Mississippi River. I can remember (as still happens today) barges chugging up and down the river. The county I am from is the largest grower of horseradish in the world, and down the street from me (once you cross the railroad tracks, which a method of mass transportation) was a large fishing lake. Even as a kid I thought, "There's a lot of stuff here." Imagine what the early Americans thought - "Game! Fish! Riches just lying there if you just develop it!"
I used to sit on my front porch, even as a teen, and wonder about everything I was looking at. I could see the smoke from the steel mill down the street. Or the power lines that transported electricity. The brick house I lived with, with central AC and gas heat. All created by those investigating all those frontiers.
There is still frontiers even today. The ocean, about which even today we still know little. And space. There's always frontiers, except today they require advanced technology.
I used to wonder why other cultures didn't find and develop North and South America. Not any more.
The Chinese, the Muslims, the Indians (dot, not feather) should have developed technology sufficient to explore the world. But they didn't. Instead they went backwards - a lot. And they went backwards on purpose. That's what the "elites" decided. And it was the common man who paid for it.
Those cultures were ruled by the parasitic 1%, who sucked up the wealth of the productive people, leaving them impoverished, so they could live in idleness and luxury. They had centralized, oppressive states.
Europe, instead, had hundreds of decentralized kingdoms. If you didn't like one, move to another. And if you still wanted more, the time came you could move across the Altantic to the Americas. Millions did, including my Scots-Irish-German ancestors. And somehow, the Scots-Irish ones ended up moving from Appalachia to the Midwest. I have no idea what they were looking for - new opportunities, I suppose.
There will always be frontiers, for those who seek them.