How did the transportation revolution , the Louisiana Purchase, and Manifest Destiny all contribute to the changing of the United States landscape by the late 1860s?
The transportation (and we might add communications) revolution, the Louisiana Purchase, and the development of the idea known as Manifest Destiny were what might be called mutually reinforcing developments in the settlement of the West in the nineteenth century. The Louisiana Purchase, concluded in 1803, led to the acquisition of the vast landmass between the Mississippi River and the Rocky Mountains. Manifest Destiny, the idea that the United States should claim all of the North American continent to the Pacific Ocean, contributed to the conquest of the American Southwest, including California, after war with Mexico in 1848. So these developments contributed to the acquisition of land in the West. The transportation revolution, which in the West mainly involved the construction of railroads, made it possible to profitably settle the vast region by connecting it to eastern markets. The effects of all of this on the landscape of the West were profound. Mining and timber companies staked out vast claims throughout the West, engaging in practices that permanently altered (we might say ruined) their environments. Farmers plowed up massive plots on their homesteads on virgin prairie lands. Railroad companies built lines that crisscrossed the West, blasting their way through mountain ranges in the process. Hunters nearly annihilated several species, most famously the buffalo that roamed the Great Plains. So the effects of these developments on the landscape of the West, and of course the peoples that lived there, were profound and irreversible, and they were well underway, if not fully realized, by the late 1860s.