Lewis and Clark were almost secretly murdered by the Spanish Empire.
https://www.npr.org/2010/04/28/126363998/the-man-who-double-crossed-the-founders
https://www.npr.org/2010/04/28/126363998/the-man-who-double-crossed-the-founders
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.
Wilkinson also recommended that the Spanish build huge defensive lines to prevent American expansion westward after the Louisiana Purchase — again, advice that Spain acted upon.