Gracia Real de Santa Teresa de Mose, or Fort Mose (pronounced MOH-say), was established in 1738. It is now considered the first free black settlement in what would become the United States of America. Alternatively spelled Mosa, Moosa, Mossa, and Moze — translated to moss in all respects — Mose was the last stop on the original Underground Railroad, which began in the South and pointed not north but further south, toward a pine forest on a swamp facing the Atlantic Ocean. To the edge of St. Augustine.

No discussion about Fort Mose opens without Francisco Menendez (no relation to Pedro Menendez de Aviles). Menendez was a Mandinga boy captured in his West African home and enslaved in the British colony of South Carolina. He had twice escaped from slavery, disappearing into the coastal swamps of Carolina and Georgia, where he lived for years among the Yamasee Indians and led his first successful military campaign against his former masters in the Yamasee War. Menendez was fated to become the revered captain of the free black militia in St. Augustine, and a founding member of Fort Mose.

In 1725, a group of runaway slaves turned up in St. Augustine seeking refuge in the rumored Spanish sanctuary state. They had fled Charleston, South Carolina, after word spread of a royal decree from the Spanish king that promised liberty to all fugitives who came to Florida seeking Catholic conversion. They were led by Francisco Menendez (given that name in baptism once he arrived in Spanish territory, his birth name is unknown). Unlike their neighbors to the north, Spain had largely attenuated their slavery practices by the turn of the 18th century. Historian Jane Landers notes in her seminal book Black Society in Spanish Florida that runaway slaves from British plantations had been fleeing to Florida since the late 17th century. The first documented runaways from Carolina made it to St. Augustine in 1687. And then again in 1688, 1689, and 1690.

Mixed societies, which included a free black class, had long existed in Spain, a precedent commonly attributed to the Moors’ occupation of the Iberian Peninsula. Landers also points out by the time Mose was founded, free black towns in the Spanish colonies of Panama, Venezuela, New Spain, and Hispaniola had already been established and received a royal sanction.

Yet it was not uncommon for runaways, or “maroons,” to be re-enslaved once they reached Spanish territory. In messages directed at the Spanish crown, Francisco Menendez wrote it was unacceptable that only some fugitive slaves had been freed when others hadn’t, even if the conditions of Spanish slaveholders were favorable to the chattel slavery of the British. In their conversion to Christianity, runaways had upheld their end of the bargain.

Not until March of 1738 did Manuel de Montiano, the 41st colonial governor of Florida, officially free all runaway slaves and establish Fort Mose to house the burgeoning numbers of fugitives arriving in St. Augustine, a result of Menendez’s persistent petitioning. Governor Montiano installed Menendez as the captain of the free black militia and the de facto leader of the fort. An obvious choice, Menendez spoke four languages and held a decorated military dossier. He chose his lieutenants. Residents of the fort were referred to as his “subjects.”

None of this is to say the settlement was some great expression of Iberian altruism. Delivering a man from slavery under strict military and religious pretenses is just another variation on enslavement. And, in a sense, recognizing and writing policies as a response to the condition of slavery is to validate something that should otherwise be considered arbitrary. Fort Mose can best be understood as a creative solution to a litany of colonial problems that marred Spanish Florida. In no small part, the settlement owed its existence to the ongoing competition between Spain and England for control of the Southeast. A stated goal in inciting runaways was to disrupt the British slave economy, but also to use the black militia as a parapet against potential invasions. As such, tentative freedom for the enslaved class of the Carolinas — which by 1700 vastly outnumbered the white planters—was within reach, just across the St. Marys River and into North Florida.

British slaveholders were fully aware of the so-called sanctuary settlement in St. Augustine and the Indian guides who led runaways there. South Carolina slave revolts in 1711 and 1714 were blamed on the Spanish, as was the infamous Stono Rebellion in Charleston in 1739, one year after Mose was founded. Carolina planters responded to slave uprisings with increased repression. Harsher bills were passed to prevent rebellions. British planters paid Indian, white, and black slave catchers to track and kill escaped slaves “whose owners were then compensated from public funds,” as Landers notes. Captain Caleb Davis, a slaveholder from Port Royal, South Carolina, turned up in St. Augustine to recover two dozen of his slaves, who had successfully escaped to Spanish Florida. Governor Montiano refused. Davis’s former slaves reportedly laughed him out of town.

These provocations would inevitably culminate in armed conflict. Governor James Oglethorpe of the newly formed Georgia territory invaded Florida in 1740, heading straight for Mose. Residents of the fort retreated to St. Augustine and were locked within the throwing-star-shaped Castillo de San Marcos, the oldest masonry fort in the U.S. The Castillo thwarted two bombardments during Spanish occupation and “still stands today, its dank gray walls brooding over the city it saved,” as Florida’s preeminent historian Michael Gannon wrote. Its porous, coquina-shell bulwark swallowed British cannonballs like marbles in Jell-O.