Hundreds of thousands of undocumented immigrants ride Mexico's 'train of death' every year to get to America

• More than 400,000 immigrants tried to enter the US undocumented through the southwestern border in 2016. The vast majority were from Central America.
• Most Central American immigrants travel along the same dangerous route, known as El Tren de la Muerte ("The Train of Death").
• Photographer Michelle Frankfurter spent years documenting immigrants traveling along the route.

Photographer Michelle Frankfurter had spent years traveling to Mexico and Central America as a photojournalist and human-rights worker. During her travels, she heard about a particular route that immigrants take to reach the US undocumented.

In 2009, she set out to follow it.

Following the path described in Sonia Nazario's award-winning book "Enrique's Journey," Frankfurter headed to southern Mexico and followed the path north.

In six journeys, she rode the treacherous El Tren de la Muerte ("The Train of Death"), came into contact with drug cartels, and befriended numerous migrant families, many of whom never made it to the US.

Frankfurter has shared some of her photos with us here, but you can check out the rest at her website or in her book "Destino," available now.