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The north-south line separating the west from the east shows a change in policy as western expansion progressed: a newly assertive federal government, the beginnings of the US conservation movement, and an admission that areas like the Great Basin could not be developed for small-holder agriculture.

Notice the swath of private land surrounding the path of the inter-continental railroad (today also the route of I-80): a trace of mid-nineteenth-century land grant policy, a development strategy that would not be repeated at such a scale in the west.