The Fur trade was of significant importance in the establishment of St. Louis. Pierre Laclede began trading furs here with the American Indians in 1764. William Clark and Meriwether Lewis described beaver populations in the west that led to fur companies organizing in St. Louis. By 1845 the heyday of mountain men ended because the demand for felt by hatters stopped and the beaver was practically trapped to extinction.
The oldest known building in St. Louis, dating from early fur trading times, was built on the land where Jefferson National Expansion Memorial is currently located. Built by Manuel Lisa in 1818, it was used to house furs of buffalo, deer, badger, skunk, and beaver. The Old Rock House was disassembled and partially reconstructed in the St. Louis Revisited Gallery at the Old Courthouse. The Old Rock House symbolizes St. Louis' first industry.
Iron mining circa 1854 brought St. Louis into a manufacturing age. St. Louis produced stoves and ornamental pieces for homes and fences created from iron. By the 1880s, the steamboat had ruled the rivers for thirty years and was in decline as a transportation mode. The steamboat faithfully transported overlanders up the Missouri River to Independence, Missouri for their journey along the Oregon Trail. By the 1920s railroads criss-crossed the United States. The iron horse had quickly put the steamboat out of commission.
In 1930, the City of St. Louis moved the courts out of the Old Courthouse. Around this time, Luther Ely Smith and other civic leaders proposed the establishment of a memorial to honor Thomas Jefferson's role in the westward expansion movement and encourage urban renewal in St. Louis. The Jefferson National Expansion Memorial was established in 1935 and the Old Courthouse was incorporated into the site in 1940.
World War II was an economic boon for St. Louis because 40% of United States small arms were produced at Weldon Springs Ordnance Plant. Post war housing shortages promoted urban flight to the suburbs. The buildings in the core of the City of St. Louis began to decay and commerce downtown was moving out of the city.
In 1948 Eero Saarinen won $225,000 in an architectural competition to develop the memorial area. He designed the Gateway Arch for Jefferson National Expansion Memorial, which encompassed the original historic district. Before any demolition at the memorial site, the National Park Service researched, surveyed and photographed structures of historical significance. In accordance with this urban renewal concept, the area surrounding the memorial grounds was designed to include a stadium, motels, offices, and commercial buildings.
The Gateway Arch structure was completed in 1965. The Museum of Westward Expansion, located in the visitor center below the Gateway Arch, was opened to the public in 1976. The Old Courthouse underwent several renovations since 1940 and was opened with exhibits in 1943. In 1979 a new museum exhibit plan was developed that established the Old Courthouse's current galleries.