Years ago my research on the records on the tribes revealed to me that George Gibbs was a significant part of the history of the tribes at the time of the treaties. An early ethnographer and Chinuk Wawa speaker and a translator for both the Oregon and California treaty commissions, he was highly influential in his time. At one point in my research I encountered some language texts he collected in Northern California. They were full of Chinuk wawa (Chinook Jargon) even though they were labeled Athapaskan. I wonder if he did not use Chinuk Wawa when speaking with the Northern California Tribes in the treaty negotiations. He had learned Chinuk Wawa earlier when employed as a surveyor for the U.S. military and stationed at Astoria. If so this expands the area in which the language was spoken much further south than previously theorized.
There is a linguistic discussion about the formation of Chinuk wawa. Some linguists feel that it was developed because of the fur trade. Others believe it developed well before the fur trade. I fall on the latter side as the tribes of the Columbia had to communicate with other hundreds of tribes who had unintelligible languages, so there was already a need well before the fur trade. But I also believe the fur trade helped spread the language and it became the most widely spoken language from San Francisco to Alaska for a few decades. Everyone spoke it, whites, Russians, Spanish, Hawaiians, Indians, everyone.
Some years ago (2000), I had a discussion with Dell Hymes and another linguist on the linguist listserves. I suggested that Chinuk wawa was used in a wider region than previously known or thought before. I suggested that specific words of the language, or part of the language could have been used quite widely for inter-tribal trade, without everyone having to be fluent in the language. Hymes agreed with this notion.
In California, I really think that Gibbs used Chinuk Wawa when speaking to Tribes in Northern California, especially that area north of the Klamath River. This includes the Tolowa, Yurok, Karok, and others. I just today found a report that says nearly the same thing.
This is from the 1851 Report of the Commissioner of Indian Affairs, page 499 (Google Books). The confirmation here means that we need to rethink the language and its broader use throughout the region.