29 photos that show the US-Mexico border's evolution over 100 years

Migrants, including a pregnant woman, wait for inspection to cross the US-Mexico border, circa 1950s. Getty Images

One of the Trump administration's latest immigration policies has come under fire, after Homeland Security figures revealed that ICE is separating families at the US-Mexico border.

Between May 5 and June 9, border officials separated more than 2,300 children from 2,206 parents, the DHS said Tuesday. The policy, Attorney General Jeff Sessions announced in early May, enforces "zero-tolerance" regulations on those who enter the US without documentation. Any migrant who attempts to cross the southern border — even those seeking asylum — is now being prosecuted.

Following mounting pressure from both sides of the aisle, Trump signed an executive order that he said will stop family separation at the border. But the fate of immigrant children already in custody remains unclear, and the order still faces legal obstacles.

The goal of establishing a firm physical boundary to separate the US from Mexico is nothing new. In the country that has the world's largest immigrant population, American presidential administrations have tried tightening security along the border for around a century.

Though the divide was formally established in 1824, the US didn't launch its official Border Patrol until 1924. Inspection and holding stations were created after that, followed by the construction of miles of fences with barbed wire and steel barriers over the next few decades.

Take a look back at the history of the US-Mexico border below.