These days, debates over immigration may seem like an inescapable and constant part of American politics. From the Supreme Court to thePresidential election, everyone has an opinion about how to fix a system that many perceive as broken.
But as immigration historian David Reimers tells TIME, that’s not actually the case. The current debate over immigration–especially when it comes to immigration from Mexico—is largely a product of the 20th century. “For so much of our history, immigrants just sort of came in,” says Reimers, a professor emeritus of history at NYU. “We had a very loose border with Mexico.”