Contributor(s): Professor Philipp Ager | The 1920s border closure is one of the most fundamental changes to United States immigration policy in the past century. In the early 20th century, European immigrants faced few restrictions for entry into the US and close to one million immigrants arrived on the nation's shores each year. This era of open immigration ended in the 1920s with a series of increasingly restrictive immigration quotas, eventually limiting entry from affected countries to 150,000 a year. Professor Ager will discuss the socio-economic consequences this policy had for the US population at that time, and what lessons can be learned from it.