Plan de la Ville de St. Louis des Illinois sur le Mississippi, avec les differente
projects de la fortifies. Map by Goerge de Bois St. Lys, 1796.
Courtesy Missouri Historical Society

More Information on Fort San Carlos and the Battle of 1780:

As soon as the British received the eastern part of Louisiana in 1763 as part of the settlement of the Seven Years War with France (called the French and Indian War in America), they imposed a treaty line which forbade English settlement west of the Appalachian Mountains (the Treaty of Fort Stanwix). This was done to accommodate the American Indians who were concerned about the ever-growing number of English and German settlers in the British colonies. But during the 1770s, English colonial explorers including Daniel Boone and Simon Kenton violated the British treaty line, moving into Kentucky and Tennessee and establishing illegal settlements there. When the American War for Independence began, one of the many grievances felt by the English colonists against their "mother country" was the official prohibition of western settlement.

During the Revolution, particularly after the French became open allies of the Americans in 1778, the Spanish began to provide covert aid and supplies to the English colonists. The Mississippi Valley became an area of scattered British outposts, illegal American settlements, and official Spanish/French mercantile towns such as St. Louis. The entire area was sparsely settled by Europeans, and in a time of conflict was considered "up for grabs."

In 1778 and 79, Virginia's George Rogers Clark campaigned in the Mississippi Valley against the British outposts. Eventually, running low on supplies, Clark came to St. Louis to ask the Spanish Lieutenant Governor, Fernando DeLeyba, for help. Upon their first meeting, each man was surprised by the other. When Clark met DeLeyba, he expected a stuffy bureaucrat, and remarked that he had "never before [been] in Compy of any Spanish gent." Clark continued by saying that DeLeyba was not reserved and had entertained him well. For his part, DeLeyba had expected a wild, unlettered frontiersman, but instead took to the open and friendly Clark immediately. DeLeyba described putting on a party which lasted two days. "Dances were given for him both nights and a supper to the ladies and the dancers, and lodging in my house with as much formality as was possible for me." Leyba urged the St. Louis merchants and traders to advance supplies to Clark on credit. Many went broke in doing so. Tensions increased as some of Clark's men, encamped at Cahokia and Kaskaskia, deserted and caused trouble in St. Louis and Ste. Genevieve. In 1779 Spain, after years of covert help to the American cause, entered the war against England as an ally of France. [Spain never openly allied with the Americans]. Spanish Royal Governor Galvez sent reinforcements to St. Louis, then attacked and reduced British posts on the lower Mississippi.

In St. Louis, Fernando DeLeyba, learning that his country was at war, urged the construction of a series of four stone towers and entrenchments to protect the town. Many St. Louisans thought such preparation foolish, and did not want to invest money in it. They were convinced that St. Louis would never be attacked, that life would go on indefinitely the way it always had. But DeLeyba pushed for money and laborers. At the top of a hill at the corner of today's Walnut and Broadway, the first of the towers, called Fort San Carlos, was completed by April 1780, and a trench was dug around the town. DeLeyba knew an attack might come soon. His health was failing, his wife had already died here in the wilderness, and all he wanted was to take his two young daughters back to Barcelona. Instead, tensions mounted in St. Louis, which was wide open to attack and protected by only 16 Spanish soldiers and the able-bodied men of the town.

On May 26, 1780, between 1,300 and 2,000 British-led Sioux, Sac, Fox and Winnebago warriors suddenly fell upon the unsuspecting community of 900 people. The Indians killed several settlers and slaves who were tending their fields on the outskirts of town. The firing alerted St. Louis's militia, who ran to the barely-completed entrenchments. The attackers were hit with a withering fire from militia musketry. But it was the cannon placed in the tower called Fort San Carlos which decided the Indians upon retreat. The battle lasted for two hours, with 21 villagers killed and 71 captured. George Rogers Clark and his Americans drove off a simultaneous British attack against Cahokia on the east side of the river. Several good citizens were buried in the churchyard that week. The successful if costly defense of St. Louis prevented the British from obtaining control of the Mississippi River Valley. The St. Louis battle was fought by the predominantly French citizens under a Spanish governor and a small number of Spanish troops, African-American slaves, and a smattering of American settlers. No further attempts were made to take St. Louis from the Spanish. Sadly, the real hero of the battle, Lieutenant Governor DeLeyba, died of illness one month afterward. He had provided defenses for a defenseless town and saved the Mississippi River Valley from British control, but never saw Barcelona again.

Meanwhile, in a series of brilliant campaigns, Bernardo de Galvez took Mobile from the British in 1780, and Pensacola in 1781. By 1781, British power in the western theater had been nullified by the efforts of George Rogers Clark and the Spanish under Galvez.