During one great period of immigration -- between 1891 and 1920 -- our nation received some 18 million men, women and children from other nations. The hard work of these immigrants helped make our economy the largest in the world. The children of immigrants put on the uniform and helped to liberate the lands of their ancestors. One of the primary reasons America became a great power in the 20th century is because we welcomed the talent and the character and the patriotism of immigrant families.