It might seem like America’s massive immigration system has always been around. But it hasn’t. Indeed, up until the early 20th century, America’s immigration system was so different it would be unrecognizable from a modern perspective. For the backstory of how the U.S. has approached immigration, we talk with Katherine Benton-Cohen, an associate professor at Georgetown and author of “Inventing the Immigration Problem: The Dillingham Commission and Its Legacy.”