Indian Sign Language
In addition to the Chinook trade jargon, Native American diplomats and traders bridged the linguistic barriers around them with a language of signs. This sign talk was not based on a particular tribe’s language but was an independent system of communication.
At the time of Lewis and Clark it was well established in the Indian country and was probably the reason why the American commanders recruited George Drouillard, the half-Shawnee hunter and interpreter, to be a civilian member of the expedition.
Opposite are images depicting the speech made in signs by Hidatsa leader Lean Wolf to Indian Office officials in Washington, D.C.:
"Four years ago the American people agreed to be friends with us, but they lied. That is all. "
Garrick Mallery. Sign Language Among North American Indians
Compared with that among Other Peoples and Deaf Mutes, 1879-80.