Some historical controversy clouds the achievements of Antoine Laumet de Lamothe Cadillac (1658-1730), a French adventurer who in 1701 founded the first significant European post west of the Allegheny Mountains and named it Detroit. The letters that Cadillac left behind give evidence of a spirited, determined, and ambitious man, and those written about him during his era reveal that these same qualities earned him an abundance of enemies.

The very name "Cadillac" was mired in debate for many years, but historians now believe that the explorer was not of noble French birth as he claimed, but simply adopted the "Lamothe Cadillac" surname when he arrived in North America. Instead he was born Antoine Laumet in 1658 in the village of St. Nicolas-de-la-Grave in southern central France, and hailed from relatively prosperous local families on each side of his parentage; his father was a local magistrate. It is thought that Cadillac...