The Underground Railroad’s Southern Branch

Every student learns about how escaping slaves received assistance while fleeing north, to the point where this informal system became known as the “Underground Railroad”; anywhere from 30,000 to 100,000 fugitives ran to the north this way. But what is recently coming to light is how approximately 3,000 to 10,000 also escaped south to Mexico and Spanish Florida.

This little-known historic fact is being brought to light in “South to the Promised Land” by Richard Grant in the July-August 2022 issue of Smithsonian Magazine, and the book South to Freedom: Runaway Slaves to Mexico and the Road to the Civil War by Alice L. Baumgartner.

The story actually begins in 1693, when King Charles II of Spain declared fugitive slaves would be free in Florida. The rule was amended in 1733 — fugitives had to convert to Catholicism and pledge loyalty to Spain. Then this policy was extended to all of New Spain in 1750, which would be Mexico and almost all of the West in addition to Florida.

In 1821, Mexico won its independence from Spain. It opened its northern state of Tejas (today’s Texas) to Anglo settlers. The problem was many migrants brought Black slaves, which the Mexican government made illegal in 1824. That and other restrictions played a big role in the 1835 revolt, and Texas’s independance in 1836. “It’s controversial, especially in Texas, but the historical profession is coming to a consensus that slavery was an important part of the Texas Revolution,” says Baumgartner.

Then in 1849, Mexico decreed that foreign slaves would become free “by the act of stepping on the national territory.” As word of this spread through the southwestern U.S., several different routes to Mexico evolved. The terrain was forbidding, especially the 100 to 150 mile-wide strip between the Nueces and Rio Grande Rivers. Some survived the long journey, only to drown in the Rio Grande. But others were armed and on horseback to outdistance their pursuers, and there was some help along the way.

This is another case of a little-known aspect of history being revealed. From the description of Baumgartner’s book on —

“…historian Alice L. Baumgartner tells the story of why Mexico abolished slavery and how its increasingly radical antislavery policies fueled the sectional crisis in the United States. Southerners hoped that annexing Texas and invading Mexico in the 1840s would stop runaways and secure slavery’s future. Instead, the seizure of Alta California and Nuevo México upset the delicate political balance between free and slave states. This is a revelatory and essential new perspective on antebellum America and the causes of the Civil War.”

“South to the Promised Land” by Richard Grant can be found at (

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