A school existed as early as the 1760s; students boarded with local families. Because habitants did not practice fertilization, the soil became exhausted. In addition, an increase in population meant there was not sufficient land for everyone. Some villagers moved to the west side of the Mississippi and founded Ste. Genevieve about 1750, in present-day Missouri. They quickly created an agricultural community with characteristics similar to Prairie du Rocher. British rule Following their victory in the French and Indian War (also known as the Seven Years' War), the British gained possession of French lands east of the Mississippi, excluding New Orleans. The Treaty of Paris was signed in 1763; however, the British did not arrive in force until 1765. To avoid British rule, many of the town's French residents moved across the Mississippi River to towns such as Ste. Genevieve and St. Louis in what was now, via the secret Treaty of Fontainebleau, Spanish Louisiana. Additionally, King George III's Royal Proclamation of 1763 designated all the land west of the Appalachians and east of the Mississippi an Indian Reserve. He tried to prevent settlers entering from the then-British Colonies. American Revolution During the American Revolutionary War, George Rogers Clark captured Prairie du Rocher for the colonies in his Illinois campaign that also resulted in the capture of Vincennes, Indiana. Reportedly, his campaign caused some of the remaining French settlers to emigrate to the Spanish-controlled territories west of the Mississippi, leaving relatively few in Prairie du Rocher. Many of the subsequent settlers of the area had been members of Clark's campaign, or were related to someone who was. They were convinced of the promise of the area by tales of the fertility of the soil in the area now called American Bottom. 1993 floods Prairie du Rocher was one of the few towns along the Mississippi River that escaped being flooded in the Great Flood of 1993. After levees broke to the north near the towns of Columbia and Valmeyer, Illinois, flood waters engulfed Fort de Chartres. They also threatened the town of Prairie du Rocher. With only the Prairie du Rocher Creek levee protecting the town, residents discovered a unique situation had developed. The water that had broken through the main Mississippi River levee and was approaching the top of the Prairie du Rocher Creek levee was higher than the water in the main Mississippi River channel. The Army Corps