No written history of the area that is now O’Fallon exists prior to 1673. The first recorded presence of Europeans in St. Charles County occurred in June of 1673 when Father Jacques Marquette and his companion, Louis Joliet, discovered the muddy waters of the Missouri River flowing into the Mississippi. The French claimed the territory that the Missouri River drained into and by the 1770’s a few French settlers were living in St. Charles County, following the paths of the earlier French fur traders.
In 1770 France formally surrendered possession of Upper Louisiana to Spain. The Spanish continued the fur trading policies of the French and established their own territorial government but Spain’s formal control of the area was weak. The territory was returned to France for a short time from 1800 until the Louisiana Purchase when the territory officially came under American control.
In the late 1790’s Anglo-Americans started crossing the Mississippi River into what is today St. Charles County. Most of them came from Kentucky, Tennessee and Virginia.
The French inhabitants of St. Charles County preferred the fur trade to farming which, according to Meriwether Lewis, they regarded as a “degrading occupation.” The American settlers from Kentucky and the other states of the upland south were much more interested in agriculture. Daniel Boone, his wife, children, adopted children, and other family members migrated to southern St. Charles County where his oldest living son held a land grant from 1797. Daniel Boone was invited by the Spanish government to migrate to this area they called New Spain along with a number of other settlers with the promise of large tracts of land should he encourage other families to migrate as well.