John Fritze, David Jackson, et al., USA TODAY, March 29, 2019

President Donald Trump on Friday threatened to close the southern border as soon as next week if Mexico doesn’t “immediately” step up its efforts to block immigrants attempting to enter the U.S. illegally.

“If they don’t stop them, we will keep the border closed,” Trump said during a stop in Florida, where he is touring Lake Okeechobee. “And we will keep it closed for a long time. I’m not playing games.”

Similar threats in the past have raised questions over the authority of the president to seal the border, the logistics of such an endeavor, and the widespread consequences it would have on Americans’ ability to trade, travel and even eat.

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Trump administration officials have sought to characterize the situation at the border as a crisis, even though apprehensions along the southern border are at historic lows.

Border Patrol routinely apprehended more than 1 million people a year – peaking at 1.6 million in 2000 – throughout the 1980s, 1990s and 2000s. In 2017, the agency apprehended just over 300,000. It 2018, it apprehended just under 400,000.

On the other hand, border officials have reported an increase in migrant families. The Trump administration this week began releasing families from custody because processing centers can’t cope with the large increase.

In the first five months of the fiscal year, agents in Yuma, Arizona, have apprehended 17,578 migrants traveling as a family. By contrast, in that same time period last year, they encountered 5,319 migrants. That’s a 330 percent increase.

Department of Homeland Security Secretary Kirstjen Nielsen hit that theme Friday.

“We face a cascading crisis at our southern border,” Nielsen said in a statement. “The system is in freefall.”

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Previous examples of closing the border are rare.

President George W. Bush partially closed the southern border following the 9-11 attacks, requiring full inspections of every incoming pedestrian and vehicle that led to days-long waits. President Ronald Reagan temporarily closed ports of entry along the southern border in 1985 following the kidnapping and murder of a DEA agent in Mexico.