How did westward expansion affect Native American nations?

Long before wagons rolled west, the land we now call the United States was already full — full of nations. Not empty wilderness waiting to be "discovered," but hundreds of Native peoples with their own languages, laws, farms, and stories, each rooted in a homeland they had known for thousands of years. This is the story of what happened when a new country decided to grow westward across those homelands.
As the young United States grew, its leaders wanted more room — more land for farms, towns, and railroads stretching toward the Pacific Ocean. They began signing treaties with Native nations. A treaty is a promise written down between two governments, like a contract. The deal usually went: Native nations would give up some land, and in return keep the rest forever, plus payments and protection.
