Despite having heard of Benedict Arnold in grade school, I only this morning learned of the traitor General James Wilkinson (thanks to NPR). Perhaps most nefariously (for a St. Louis resident) he betrayed explorers Lewis and Clark to the Spanish.
"As a spy, his tradecraft was excellent. Wilkinson sent his information in a code — just rows of numbers in groups of four," Linklater says. "It was never broken."
Through these coded messages, Wilkinson informed the Spanish of the Lewis and Clark expedition and its secret goal of finding a land route through the Western mountains and to the Pacific Ocean. He suggested that his paymasters send armed patrols to intercept the expedition — which the Spanish did.
"Only by the grace of God did they fail to find them," Linklater says. If the Spanish patrols had been luckier or more skillful, we might remember Lewis and Clark — if we remembered them at all — as two explorers who vanished in the West. And the course of American history might well have been dramatically altered.