Jean Baptiste Bénard de La Harpe, trader, explorer, and soldier, was born in late January or early February 1683 in Saint-Malo, France, one of twelve children of Pierre Bénard and Jeanne (Le Breton) Seigneur de La Harpe. In 1701 he was appointed a cavalry officer in a regiment of Philip V of Spain, but served only a short time before returning to Saint-Malo. In 1703 he sailed to Peru, where he married, on February 7, 1705, a wealthy widow, Doña María de Rokafull, the former Marie de Witte Solier of Flanders, twenty-two years older than he. La Harpe worked as a merchant in Peru and misrepresented his fortune to his future wife. Around 1706 he wrote an account, referred to as his Relation, of his South American experiences, but it has been lost. His wife described the book as fiction. The couple returned to France in January 1706, and shortly thereafter María began efforts to have the marriage annulled. She died in 1709, but La Harpe's legal battle for her money lasted until 1715; he lost all suits brought by her heirs. La Harpe was married again on September 9, 1710, to Jeanne Françoise Prigent de Penelan; it is believed that she died soon, perhaps by 1715. In the meantime he had purchased the largely honorary titles of governor of the town of Dol and lieutenant general of the coast guard in Brittany. These titles were soon abolished, and he decided to leave France.
La Harpe and about forty persons set sail on the ship Victoire from La Rochelle, France, in the spring of 1718 and arrived at Dauphin Island, off the coast of what is now Alabama, around August 27, 1718. Some sources state that La Harpe may have held a concession of four square leagues in Louisiana on the Red River, while other reports mention six small concessions possibly held by him and his associates. The men went to New Orleans in the fall of 1718 and left there on December 17 of that year with orders from France to settle along the Red River. La Harpe, as a concessionaire for the Company of the Indies, set out to establish a trading post and explored the Mississippi, Red, and Sulphur rivers. In April 1719 he established Fort Saint Louis de los Cadodaquious (also called in various sources San Luis de Cadodachos and Fort Breton). Its approximate location was said to be near an old Nasoni village at Roseborough Lake, a cut-off branch of the Red River now in Bowie County. La Harpe wrote Governor Martín de Alarcón and Father Antonio Margil de Jesús to propose a trade alliance with the Spaniards. However, French and Spanish opposition in the War of the Quadruple Alliance and a French raid of San Miguel de Linares de los Adaes Mission ended any prospects. In the summer of 1719 La Harpe continued his exploration, planning to visit the Comanches. His precise course is unknown, but he may have gone along a branch of the Canadian River in Oklahoma. The following fall he returned to the Red River and, after stopping for three weeks because he was ill with fever, arrived in New Orleans on January 26, 1720, and returned to France.
On November 9, 1720, La Harpe was appointed commandant of La Salle's Saint Bernard Bay (Matagorda Bay) on the Texas coast. In April 1721 with fifteen soldiers he set sail on the ship Subtile, captained by Jean Béranger, with François Simars de Bellisle as ensign. La Harpe was to establish a post at Saint Bernard, but on August 27, 1721, believing they had arrived at their correct destination, the men sailed instead into Galveston Bay. Resistance by Indians made this venture unsuccessful. By March 1722 La Harpe explored up the Arkansas River with the intention of opening trade routes to the Spanish Southwest, but was turned back by supply problems. He returned to France in 1723, discharged by the Company of the Indies, and never returned to America. His Journal historique concernant l'établissement des Français à la Louisiane, about his experiences in America, was published in 1831. Both La Harpe's contemporaries and modern historians have speculated that some of his accounts were either based on hearsay or exaggerated. He died in Saint-Malo on September 26, 1765.