It really all comes down to money.
The perfect illustrative example of this would be the Department of Education. States have the power to enact their own education policies and nowhere is education laid out as a federal duty. And yet, a Federal department exists.
They enter by setting policies and giving enough money to the States to follow the federal policies.
Growth of the railroads.The government gave the railroad companies huge amounts of land for every mile of track laid. This land was used to develop new towns and cities, greatly reducing the area of free pasturage available to cattle owners for their herd.
Increasing numbers of new immigrants. Many of these European immigrants set up as sheep farmers, which required much less capital investment than cattle farming. The sheep farmers fenced off their land, further reducing available free pasturage for cattle, and additionally denying access to vital water sources for the cattle herds.
