The Spanish authority became regularly established in Upper Louisiana, in November, 1770. Piernas, the Spanish commandant, arrived in St. Louis at that date, but there is no official document or record to show that he exercised the functions of his office previous to February, 1771. Other towns or villages were settled in the vicinity from 1769, the date of St. Charles, to the period of 1780.
On the transfer of the Illinois country from France to Great Britain in 1765, many of the French inhabitants removed from that side of the river to St. Louis and St. Charles, and many more went down the river to the lower province.
After Colonel George Rogers Clark had taken possession of the Illinois country, under Virginia, in 1778, he became personally acquainted and held frequent interviews with French citizens of St. Louis, and the official authorities.
While at Cahokia, in 1779, only five miles distant, holding treaties with the Indians from confidential agents whom he sent into the Indian country northward, he learned that British agents from Canada, with a large force of northern Indians, were projecting an invasion of St. Louis. Being on terms of friendly intercourse with Governor Leyba, the Spanish commandant, he gave him intimation of these treacherous designs, as he did to several French gentlemen, and tendered his services with the forces he commanded, in case of an attack. St. Louis then was enclosed with short palisades, and gates opened in the pathways that led to the common field, and to the country without. The sequel gave proof that the governor was a traitor, purchased, doubtless, with British gold.
In the month of May, 1780, a large band of warriors from different tribes of Indians from the Upper Mississippi and the northern lakes, with a number of Canadians, amounting in all to twelve or fourteen hundred armed men, appeared in the forest east of the Mississippi, above St. Louis. The 25th of May was the festival of Corpus Christi, a day highly venerated by the inhabitants who were Catholics. Had the assault been made on that day it would have been fatal to the town; for after the service in the church, nearly all the inhabitants, men, women and children, flocked to the prairie to gather strawberries, which were abundant, and delicious at that season. A few Indians had crossed the river as spies, and secreted themselves in the thickets near where the people passed.
Next day the main body crossed the river, and attacked the town. A few persons who had gone to the field, were attacked from an ambuscade; some were killed; others fled to the town and gave the alarm. The soldiers under the command of the Governor, and his subalterns, either from fear or treachery, hid themselves, and the citizens alone had to defend the place. They found some government cannon, and fired grape shot as the invaders approached the gates. A few days previous the treacherous governor sold all the public ammunition to some traders, but the people supplied themselves with eight kegs of powder they found in a trader’s house.
The governor kept within his house, but hearing the firing, and learning the citizens were making a manful resistance, he came out, ordered the firing to cease, and the cannon to be spiked and filled with sand by some of his minions. Fortunately the men at the lower gate did not hear the peremptory order, and continued the firing. The governor, perceiving this, ordered a cannon to be fired at them. They threw themselves on the ground, and the murderous volley of grape shot passed over their heads. This horrible procedure, with his general conduct, fixed the indelible brand of traitor on his name, and such the French citizens reported him to have been, to the immediate representative of the crown of Spain in New Orleans.
The inhabitants of St. Louis were in a critical situation. With evidence of treachery among the officers, who were Spanish; the place invaded by a force nearly double to the whole population, men, women and children; and these invaders infuriated with the spirit of war and plunder, what could they expect but a general massacre! But after killing and scalping twenty persons in the field and prairie, and meeting with such determined resistance at the gates, the Indians retired suddenly, and refused to coöperate with their Canadian allies, who kept themselves at a safe distance.
The cause of this sudden and unexpected retreat has been a mystery. The most probable solution is the tradition among the French inhabitants, that the Indians were told they were going on a war party to fight the Spaniards; but when they discovered the defenders of the town were all Frenchmen, and recognized amongst them some of their personal friends, who had lived and traded in their villages; and that they had been deceived by British agents, they withdrew in ill-humor with their employers.
Divers misstatements of this assault have been handed down by writers and oral tradition. A popular error has been propagated, that Colonel Clark was at Cahokia, (some say Kaskaskia) and suddenly appeared on the bank of the Mississippi, opposite the town with a strong force. Colonel Clark left the Illinois country with all the men whom he could persuade to re-enlist, the preceding February, went down the Mississippi, and at the date of the attack was establishing fort Jefferson, below the mouth of the Ohio. From thence he traveled on foot with a single companion through the wilderness to Harrodsburg in Kentucky.