Battle of St . Louis The Battle of St . Louis ( Spanish " San Luis " , also known as the Battle of Fort San Carlos ) was an unsuccessful British - led attack on St . Louis ( a French settlement in Spanish Louisiana that had been ceded by France to Spain in 1763 ) on May 26 , 1780 , during the American Revolutionary War . A force composed primarily of Indians and led by a former British militia commander attacked the settlement . The settlement ' s defenders , mostly local militia under the command of Lieutenant Governor of Spanish Louisiana Fernando de Leyba , had fortified the town as best they could , and successfully withstood the attack . A second simultaneous attack on the American outpost at Cahokia , Illinois was also repulsed . The retreating Indians destroyed crops and took captive civilians outside the protected area . The British failure effectively ended their attempts to gain control of the Mississippi River during the war . Background . Following the entry of Spain into the American Revolutionary War in 1779 , British military planners in London wanted to secure the corridor of the Mississippi River against both Spanish and Patriot activity . Their plans included expeditions from West Florida to take New Orleans and other Spanish targets , and several expeditions to gain control of targets in the upper Mississippi , including the small town of St . Louis . The expedition from West Florida never got off the ground , since Bernardo de Gálvez , the Governor of Spanish Louisiana , had moved rapidly to gain control of British outposts on the lower Mississippi , and was threatening action against West Florida ' s principal outposts of Mobile and Pensacola . British expedition . The British expeditions from the north were organized by Patrick Sinclair , the military governor at Fort Michilimackinac in present - day Michigan . Beginning in February 1780 he instructed fur traders to circulate through their territories , recruiting interested tribes for an expedition against St . Louis . The fur traders were offered the opportunity to control the fur trade in the upper parts of Spanish Louisiana as an incentive to participate . Most of the force gathered at Prairie du Chien , where they were placed under the command of Emanuel Hesse , a former militia captain turned fur trader . The force numbered about two dozen fur traders and an estimated 750 to 1 , 000 Indians when it left Prairie du Chien on May 2 . The largest contingent of the force was about 200 Sioux warriors led by Wapasha , with additional sizable companies from the Chippewa , Menominee , and Winnebago nations , and smaller numbers of warriors from other nations . The Chippewa chief Matchekewis was given overall command of the native forces . When the force reached Rock Island they were joined by about 250 men from the Sac and Fox nations . These warriors were somewhat reluctant to attack St . Louis , but Hesse gave them large gifts to secure their participation in the venture . The diversity within the expedition included some animosity among the tribes , for the Chippewa and Sioux in particular had a history of conflict with each other . However , Wapasha and Matchekewis promoted unity during the expedition . Spanish and American defenses . The village of St . Louis was primarily a trading hub on the Mississippi River , but it was also the administrative capital of upper Spanish Louisiana , and it was governed by Lieutenant Governor Fernando de Leyba , who was also a captain in the Spanish Army . Leyba was warned in late March 1780 by a fur trader that the British were planning an attack on St . Louis and the nearby American - held post at Cahokia . He began developing plans for the village ' s defense . He had only 29 regular army soldiers of the Fijo de Luisiana Colonial Regiment and an inexperienced militia force of 168 , most of whom were dispersed in the surrounding countryside . Leyba developed a grand plan of defense that included the construction of four stone towers . Without funds , or the time to get them from New Orleans , Leyba asked the villagers to contribute funds and labor to the construction of these fortification s , and paid for some of the work from his private funds . By mid - May a single round tower had been built that was about in diameter and thirty to forty feet tall . The tower , dubbed Fort San Carlos , provided a commanding view of the surrounding countryside . As there did not appear to be sufficient time to build more towers , trenches were dug between the tower and the river to the north and south of the village . Five cannon were placed on top of the tower , and additional cannon were placed along the trenches . When Leyba learned that Hesse ' s force had reached Rock Island , he called in the outlying militia and summoned reinforcements from Ste . Genevieve . By May 13 he recorded that he been reinforced by " about 150 men , all good shots " . On May 15 , Leyba was visited by John Montgomery , the American commander at Cahokia , who proposed a joint Spanish - American force to counter Hesse ' s expedition , an idea that did not reach fruition . On May 23 , Leyba ' s scouts reported that Hesse ' s force was only away , had landed their canoes , and were coming overland . Battle . On May 25 , Hesse sent out scouting parties to determine the situation at St . Louis . These parties were unable to get close to the village due to the presence of workers , including women and children , in the fields outside the village . The next day Hesse sent Jean - Marie Ducharme and 300 Indians across the river to attack Cahokia , while the remainder headed toward St . Louis , arriving about 1 : 00 pm . A warning shot was fired from the tower when they came in view , with the Sioux and Winnebagoes leading the way , followed by the Sac and Fox , and the fur traders , including Hesse , bringing up the rear . Leyba directed the defense from the tower , and opened a withering fire from there and the trenches when the enemy force came in range . On the first volley , most of the Sac and Fox fell back , apparently unwilling to fight , leaving many of the other participants suspicious of their motives in joining the expedition and complaining of their " treachery " . Wapasha and the Sioux persisted for several hours in attempts to draw the Spanish defenders out , going so far as brutally killing some captives they had taken in the fields . Although this angered some of the townspeople to the point where the militia requested permission to make a sortie , Leyba refused , and the attackers eventually withdrew and headed north , destroying crops , livestock , and buildings as they went . On the other side of the river , Ducharme ' s attack on Cahokia was easily repulsed . The timely arrival of George Rogers Clark to lead its defense played a role ; Clark ' s reputation as a frontier fighter made the Indian force reluctant to pursue the attack . Aftermath . The village of 700 lost between 50 and 100 killed , wounded , and captured , virtually all civilians . A year later the Spaniards from St . Louis raided Fort St . Joseph , bringing the captured British flag back to St . Louis . Fernando de Leyba died the following month , the subject of local criticism because he never formally recognized the efforts made by the citizenry in the town ' s defense . His valor earned him a promotion to lieutenant colonel from King Charles , who did not know that he had died . Legacy . The site where Fort San Carlos stood is at the corner of Fourth and Walnut Streets in St . Louis . A local organization annually commemorates the battle by reading the names of 21 people who lost their lives in the battle . The battle is also remembered in a mural and diorama located in the Missouri State Capitol ( pictured ) .