<P> As settlers poured in, the frontier districts first became territories, with an elected legislature and a governor appointed by the president . Then when population reached 100,000 the territory applied for statehood . Frontiersmen typically dropped the legalistic formalities and restrictive franchise favored by eastern upper classes, and adopting more democracy and more egalitarianism . </P> <P> In 1800 the western frontier had reached the Mississippi River . St. Louis, Missouri was the largest town on the frontier, the gateway for travel westward, and a principal trading center for Mississippi River traffic and inland commerce but remained under Spanish control until 1803 . </P> <P> Thomas Jefferson thought of himself as a man of the frontier and was keenly interested in expanding and exploring the West . Jefferson's Louisiana Purchase of 1803 doubled the size of the nation at the cost of $15 million, or about $0.04 per acre ($245 million in 2017 dollars, less than 42 cents per acre). Federalists opposed the expansion, but Jeffersonians hailed the opportunity to create millions of new farms to expand the domain of land - owning yeomen; the ownership would strengthen the ideal republican society, based on agriculture (not commerce), governed lightly, and promoting self - reliance and virtue, as well as form the political base for Jeffersonian Democracy . </P> <P> The $15 million paid France for its sovereignty over the territory in terms of international law . Because of inflation, that $15 million is equivalent to about $294 million in 2012 dollars . Between 1803 and the 1870s, the federal government purchased the actual land from the Indian tribes then in possession of it . 20th century accountants and courts have calculated the value of the payments made to the Indians, which included future payments of cash, food, horses, cattle, supplies, buildings, schooling, and medical care . In cash terms, the total paid to the tribes in the area of the Louisiana Purchase amounted to about $2.6 billion in current dollars, or $8.5 billion in 2012 dollars (nearly $9 billion in 2016 dollars). Additional sums were paid to the Indians living east of the Mississippi for their lands, as well as payments to Indians living in parts of the west outside the Louisiana Purchase . </P>

Who settled on the great plains during the gilded age