sentences:  In 1819, following a devastating plague of locusts which left the colonists with insufficient seed even to plant a crop, an expedition was sent by snowshoe to purchase seed at Prairie du Chien.It returned by flatboat up the Mississippi and Minnesota Rivers and down the Red River, arriving back at the settlement in the summer of 1820.In 1821, five dissatisfied settler families left the colony for Fort Snelling, the forerunners of later tides of migration up and down the valley between the two nations.