La Salle, René-Robert Cavalier de (21 November 1643–19 March 1687), explorer, was born in Rouen, France, the son of Jean Cavelier, a haberdasher, and Catherine Geest. The family was part of the prosperous bourgeoisie. The sobriquet “de La Salle” referred to an estate they owned outside Rouen. La Salle’s initial intention, however, seems to have been to escape his position, for after having studied with the Jesuits in Rouen, he renounced any claim to the family fortunes and entered the novitiate for the order in Paris in 1658. He actually took vows in 1660, continued, apparently rather brilliantly, his studies of mathematics, and taught in Jesuit schools until 1666. Having requested missionary assignments several times and been denied because he had been unable to demonstrate spiritual maturity and submission to the discipline of the order, he was released from his vows in 1667 and only a few months later went to New France, penniless but with many influential connections. There his brother, a Sulpician, was doubtless responsible for his obtaining from that order a grant of a seigneury on Montreal Island, but after two years La Salle sold most of it back to them and began his career of exploration by attaching himself to the Dollier and Galinée missionary party bound for the western Great Lakes. Hearing of the Ohio River from Iroquois Indian guides, he left the party, claiming illness, and virtually disappeared for four years....