Answer: Ireland and Germany
Explanation: Nearly 4.2 Million people left Europe mostly between 1845 and 1850, the largest immigration in U.S. history. The immigrants were mostly from Ireland and Germany. Roman Catholic peasants left Ireland because of land eviction and also in 1840s due to the famine following the potato blight. The Lutherans, Catholics, and Jews from Germany immigrated to U.S. were a mix of farmers, artisans, professionals, and traders who came to U.S. till the German industrialization created a huge demand for laborers at the homeland.