When Louisiana became part of the United States in 1803, St. Louis was a straggling frontier village, frequented mostly by boatmen and trappers. It had been established as a trading post back in 1764 by a party of French trappers from New Orleans, and had, from the first, monopolized the fur trade of the upper Mississippi and Missouri River country. Here hunters and trappers brought the spoils of distant forests. Here the surrounding tribes of Indians came to trade with the friendly French. Here countless open boats were loaded with skins and furs and then floated down the Mississippi. [Illustration: LOUISIANA PURCHASE] Notwithstanding this flourishing trade, the growth of the settlement was slow. In 1803 the population numbered less than one thousand, made up of French trappers and hunters, a few other Europeans and Americans, and a considerable number of Indians, half-breeds, and negro slaves. But as soon as Louisiana belonged to the United States, a new era began in the West. Emigrants from the Eastern states poured over the Appalachian Mountains. St. Louis lay right in the path of this overland east-to-west travel. From here Lewis and Clark started, in 1804, on their famous exploring trip of nearly two years and a half, up the Missouri River, to find out for the country what Louisiana was like. It was here that emigrants headed for the Oregon country stopped to make final preparations and lay in supplies. The remote trading post of the eighteenth century was suddenly transformed into a wide-awake bustling town. [Illustration: MISSISSIPPI RIVER BOATS] Furs were now no longer the only article of trade. The newly settled Mississippi valley was producing larger crops each year. Because of the poor roads, overland transportation to the markets on the Atlantic was out of the question, and trade was dependent on the great inland waterways. Early in the century, keel boats and barges carried the products of field and forest down the Mississippi. Then came the arrival of the first steamboat, the real beginning of St. Louis' great prosperity, working wonders for this inland commerce whose growth kept pace with the marvelous development of the rich Middle West. [Illustration: ST. LOUIS AND HER ILLINOIS SUBURBS] St. Louis, lying on the west bank of the Mississippi, between the mouths of the Ohio and Missouri rivers and not far from the Illinois, became the natural center of this north-and-south river traffic. By 1860 it was the most important shipping point west of the Alleghenies. [Illustration: THE MUNICIPAL COURT BUILDING]