Some languages are the result of wars that forced one language on another. Chinook Jargon was created during peace to enable people to work together.
It was the Esperanto of the American Indians. Even European settlers and trappers spoke this language. Some second generation settlers spoke it as their first language. It was created by American Indians on the northwest coast of North America to enable them to trade with each other. It was derived from the languages of many isolated tribes native to the area, but originally from Chinook. As the settlers arrived English and French words were incorporated into it too. The number of words in the language was only in the hundreds and its grammar was simple making it easy to learn and use. It spread quickly all the way to Alaska.
Using it in legal documents was routine. Therefore many documents created prior to the twentieth century on the northwest coast of North America contain at least vestiges of it (some say nearly all do). Cherokee often is the language of choice for American Indian ceremonies, but Chinook Jargon probably was more widely understood.