Columbus accidentally discovered the Americas while seeking a route to China. This discovery led to an exchange of plants, animals, diseases, and peoples between the Old World and the New that profoundly impacted both, known as the Columbian Exchange. Crops like potatoes from South America and sugar cane in the Americas grown by African slaves became dietary staples and drove economic and population changes in Europe and Africa. The introduction of new diseases and crops also devastated indigenous populations in the Americas. When the Irish potato crop was affected by blight in the 1840s, over a million Irish fled to North America in the ensuing famine.