In the Deep South United States, scholars are discovering a nearly forgotten piece of American history: the Underground Railroad to Mexico. Americans are increasingly interested in studying—and strongly renouncing—slavery. And that is bringing a shadowy saga into light.

American slavery is a dark blot on human history. Slavery corrupts God’s purposes, for God made each human in His own image, (Genesis 1:26–28) and He desires human unity in Jesus Christ. (Galatians 3:28)

Today, most people know the stories of Harriet Tubman, John Brown, and other abolitionists and activists. They worked on the northern branch of the Underground Railroad. That network of people and homes helped fugitive slaves flee to safety in Northern states and Canada.

Professor Roseann Bacha-Garza researches U.S. Civil War history in South Texas. She discovered that many slaves headed south to Mexico. Mexico abolished slavery in 1829, a generation before President Abraham Lincoln’s Emancipation Proclamation. Escaped slaves there could adopt Spanish names, marry into Mexican families, and migrate deep into Mexico—safely out of slaveholders’ reach.

Bacha-Garza unearthed records of folks near the border who helped the fleeing people. Her research showed that enslaved people in the Deep South sometimes took the Mexico route with help from German immigrants, Mexican Americans, and couples like the Jacksons and Webbers.

Nathaniel Jackson, a white Southerner, purchased the freedom of black slave Matilda Hicks and her family. Nathaniel and Matilda married and moved from Alabama to Texas before the Civil War. There, along the Rio Grande River, they encountered another biracial couple, Vermont-born John Ferdinand Webber and black former slave Silvia Hector. Descendants say the two families’ ranches served as stops on the Underground Railroad to Mexico.

Karl Jacoby studies ethnicity and race at Columbia University. He says slave owners often complained that their “property” was likely heading to Mexico. They offered rewards for runaway slaves. Slave-catching mobs tracked them over the border. But they were opposed by armed villagers and Black Seminoles (descendants of the Seminole people, free blacks, and escaped slaves).

In 2010, the U.S. National Park Service outlined a route from Natchitoches, Louisiana, through Texas to Monclova, Mexico. It is considered a rough path of the Underground Railroad south.

This southern branch of the Underground Railroad is just starting to enter the public’s awareness. But former Texas slave Felix Haywood told interviewers in 1936 that slaves laughed at the suggestion of running north for freedom.

“All we had to do was walk,” Haywood said, “but walk south. And we’d be free as soon as we crossed the Rio Grande.”