I was thinking about how many people in the US that live near the Mexican border consider it a very useful skill to be at least conversational in Spanish, and it made me curious if there would have been a similar mindset among different Native American tribes that were likely to encounter each other often.
Multilingualism was very common among the tribes of the Northwest. Powers (1877) noted one informant in NW California that "had 6 languages and one eye in his head". C. Hart Merriam in the early 1900s collected information from informant "Saxey" on three different languages from three different language stocks. NW California natives that lived near the boundary with other tribes were almost always at least bilingual. This is in an area where virtually every drainage was occupied by a different language group. This pattern was, to a great degree, true of other NW nations as far north as southern Alaska. Multilingualism was very important in trade and other economic and social interactions.
Powers, Stephen 1877. Tribes of California. U.S. Dept. of the Interior, Geological Survey.
Thompson, Lawrence C. and M. Dale Kinkade 1990. Languages. in Handbook of North American Indians, vol 7. Northwest. Smithsonian.