Why did the American founders use Locke’s philosophy to develop their principle of property rights? Because by using Locke’s philosophy they could make the argument that only the European population was entitled to have rights, and that the native Indians were savage beasts who did not deserve rights. In his Second Treatise of Government (1690), Locke has argued that property rights are derived from labor. Those who work on the land—by farming, building infrastructure, and setting up industry—have rights. Those who are living in a State of Nature have no rights.
Here’s a line from Locke’s Second Treatise of Government: "Whatsoever then he removes out of the state that nature hath provided, and left it in, he hath mixed his labor with, and joined to it something that is his own, and thereby makes it his property.”
The American founders asserted that the native Indians were living in a State of Nature, since they got their essential needs through activities like forging, hunting, fishing, herding, and they were not radically transforming the landscape by building large plantations, towns, and industries. The Americans claimed that activities like forging, hunting, fishing, and herding did not amount to “mixing one’s labor with the land.” The lazy natives, the Americans argued, were not “improving landlords” who would make optimal use of the land, so they had no legal claims to own the land. Thus, the land in which the natives had lived for thousands of years was deemed vacant, and was opened up for the settlement of the rising European population.
It was not true that the natives were lazy or were not working on the land. They were operating successful farms and fisheries for thousands of years before the Europeans arrived. They had built several cities the ruins of which exist till this day. They were responsible for clearing forests and building dams. All this was ignored by the American political elite—they continued to insist that the “merciless Indian savages,” who lived in a State of Nature, must be thrown out of North America and their land should be given to the European farmers and industrialists. Between 1776 to 1900 a significant part of the native population in the USA was either killed or evicted.