Political controversy(争论)about the public-land policy of the United States began with the American Revolution. In fact, even before independence from Britain was won, it became clear that resolving the dilemmas(困境)surrounding the public domain might prove necessary to preserve the Union itself.
At the peace negotiations with Britain, Americans demanded, and got a western boundary at the Mississippi River. Thus the new nation secured for its birthright a vast internal empire rich in agricultural and mineral resources. But under their colonial charters(契约),seven states—Massachusetts, Connecticut, New York, Virginia, North Carolina, South Carolina, and Georgia—claimed portions of the western wilderness. Virginia’s claim was the largest, stretching north and west to encompass the later states of Kentucky, Ohio, Indiana, Illinois, Michigan and Wisconsin. The language of the charters was vague and their validity questionable, but during the war Virginia reinforced its title by sponsoring Colonel George Rogers Clark’s 1778 expedition to Vincennes and Kaskaskia, which strengthened America’s trans-Appalachian pretensions(要求，权利)at the peace table.
The six states holding no claim to the transmountain (在山那边的)region doubted whether a confederacy in which territory was so unevenly apportioned would turely prove what it claimed to be a union to equals. Already New Jersey, Delaware, Rhode Island, and Maryland were among the smallest and least populous of the states. While they levied(征收)heavy taxes to repay state war debts, their larger neighbors might retire debts out of landsale proceeds.
Why does the author mention Colonel Clark’s expedition