Missouri River floods washed Peter Sarpy out of Traders Point, the old fur trade outpost from the days of Spanish Louisiana. Sarpy instead found the only dry crossing on that stretch of the river and established St. Mary. Sarpy's new town boomed with the steamboats from St. Louis and Nebraska's first town of Bellevue right across the river. By the end of the Civil War the river had washed away St. Mary and nothing of the town remains today.