How did Thomas Jefferson help form the American Dream?

Some might argue that Jefferson articulated the "American Dream" in the Declaration of Independence when he and the other signers asserted the "pursuit of happiness" as a fundamental right, and claimed that the United States was being established to promote that right.
But the "American Dream" was really more of a creation of the late nineteenth and early twentieth centuries—the idea that, in America, anyone could achieve material and social success with hard work and application. To the extent Jefferson promoted that vision, he did so through his commitment to westward expansion. He had a general distaste for urban manufacturing, and instead promoted the idea that the United States should be a nation of small landholders (or "yeomen") who farmed for the market. To this end, he supported expansionist measures, most notably the Louisiana Purchase, which marked the culmination of his attempts to gain access to the Mississippi River as an outlet for agricultural produce.
https://millercenter.org/president/jefferson/domestic-affairs