Most Americans know how the early 19th-century Underground Railroad conveyed an estimated 100,000 enslaved people to freedom in the northern United States and Canada.
But few know of the southern Underground Railroad, on which enslaved people walked to freedom in Mexico.
“This escape route was essential to U.S. history,” says Alice L. Baumgartner, Ph.D., an associate professor of history at the University of Southern California and author of South to Freedom: Runaway Slaves to Mexico and the Road to Civil War. “The threat of enslaved people escaping to Mexico destabilized slavery in Texas and Louisiana.”

Baumgartner says one reason the southern route is less studied is that it didn’t rely on abolitionist guides and formal safe houses that were common along its northern counterpart.
Instead, the southern Underground Railroad operated mostly through word-of-mouth among enslaved people.
Mexican laborers working in Texas, Baumgartner says, sometimes gave enslaved people directions and information about routes to Mexico. “It was much less organized than what we usually think of,” she concludes.
Mexico promised freedom before U.S.
Because Mexico abolished slavery in 1829, it became a safe place to which enslaved people could escape and start new lives.
Baumgartner first discovered the southern Underground Railroad in Mexico’s historical archives. There, she stumbled across a record of a court case where a Texas plantation owner crossed into Mexico to try to take escaped enslaved people back to the United States. The Mexican legal system denied his claim.
Also in this era, Los Mascogos, groups of organized Black Seminole (Native American) militias, guarded against owners of enslaved people who tried to assert legal rights in Mexico.
Following unknown markers
Historians and anthropologists have tried to recreate the southern Underground Railroad with minimal information and without the artifacts and landmarks of the northern route.
“The fact that we don’t have many sources about how [the route] worked and how they actually did it stands testament to how successful and remarkable they were at doing this because they didn’t leave a trace for us or their enslavers to follow,” Baumgartner said.

In 2010, the U.S. National Park Service traced a theoretical route from Natchitoches, Louisiana, to Texas to Monclova, Mexico.
A new life in Mexico
Baumgartner and other scholars have determined that 10,000 enslaved people escaped to Mexico between 1700 and 1865. During the period that Baumgartner studied, 1850–1859, she estimates that 5,000 enslaved people went to Mexico, making it the most active part of the route’s history.
Little is known about their lives in Mexico, other than that they never returned to the United States.
In a 1936 oral history, Felix Haywood — a formerly enslaved person in Texas — recalls his family’s choice between going north or going south to find freedom.
His family laughed at those who suggested going north. “All we had to do was walk, but walk south, and we’d be free as soon as we crossed the Rio Grande,” he said.
“In Mexico you could be free,” Haywood continued. “Hundreds of slaves did go to Mexico and got on all right. We would hear about them and how they were going to be Mexican. They brought their children up to speak only Mexican [sic].”
The 200th anniversary of diplomatic relations between the United States and Mexico and the observance of Black History Month provide occasions to reflect upon both slavery and the ways enslaved persons resisted it, helping to lay the groundwork for a more hopeful future.