How many migrants have died trying to cross the southwest border into the United States?

Nobody knows for sure. Thousands, at least.

People ran out of water and burned up with hyperthermia in 120-degree desert heat. Some froze to death at night. Others were hit by trains, or run over by cars in a final highway sprint. They drowned in rivers, became trapped in rock crevices, got bitten by poisonous snakes. Arizona alone has 17 different kinds of rattlesnakes, including the deadly Mohave.

Some died of illness in federal custody.

“We’ve kind of lost sight of the human cost of this, because we’re thinking about other pressing migration issues or political issues,” said Jason De León, a University of California, Los Angeles anthropology professor and author of The Land of Open Graves: Living and Dying on the Migrant Trail.

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The Border Patrol counted 7,442 deaths from 1998 to 2018, an average of 372 a year.

But that’s likely an undercount, U.S. Customs and Border Protection acknowledges, due to the multiple police and government entities that operate at the border, and the crazy-quilt of lands controlled by states, ranchers, developers, private interests, national parks, and Native American nations.

As a result, some deaths never become known to the Border Patrol, the agency said.

The International Organization for Migration, a U.N.-related agency, counted 1,905 deaths from 2014 to 2018, roughly 430 more than the Border Patrol recorded during the same time. But IOM doesn’t claim its figures are definitive.

“All existing death counts,” IOM wrote, “have gaps.”

The San Diego activist group Border Angels estimates 10,000 dead since 1994, which computes to a higher annual average than both official agencies.

People trek north from Mexico, but these days more of them are in flight from violence and poverty in Guatemala, El Salvador, and Honduras.

Some simply vanish, their fates unknown to families at home and authorities on the American side of the line. Extreme desert conditions and hungry animals that drag away bones can rapidly make a body disappear.

No More Deaths, a southern Arizona group that leaves jugs of water on well-traveled migrant paths, blames American enforcement policies for what it claims are thousands of disappearances over the last 25 years.

In the mid-1990s, the government began hardening ports of entry by adding new agents, fencing and sensors. That redirected migrants toward remote areas, into desert and mountain terrain so treacherous that authorities expected people would abandon plans for traveling before they ever left home.

“The idea [was] if people die, others will stop coming,” De León said, adding that the government misunderstood a key reality: “The threat of death in Arizona is nothing compared to death in Honduras.”