Between 1846 and 1940, more than 50 million Europeans moved to the Americas, irrevocably changing both their new lands and the ones they left behind. Their immigration fostered an idea of the "land of the free," and yet more than a third returned home again. As villages emptied, some blamed traffickers in human labor, targeting Jewish emigration agents. Others saw opportunity: to seed colonies of migrants, or to gain economic advantage from an inflow of foreign currency, or to reshape their populations by encouraging the emigration of minorities. These precedents would shape the Holocaust, the closing of the Iron Curtain, and tragedies of ethnic cleansing, while also forming notions of social solidarity, human rights, and freedom--whether it be the freedom to move or the freedom to stay home.