I've read that there are only about 800 words in the language, and no grammer to speak of. If you need to make a more complex thought, you just join two words together and count on context to make it work. I guess properly it is a pidgin - a trade language, and there are words from not just the Chinook but many other aboriginal groups (they used it all the way up to the Inuit territory and all the way down to N. California). When the voyageurs and then colonists came French words were added, and then English, Hawaiian, Chinese, it evolved organically.
At various times of my life my dad and I have tried to learn Chinook Jargon. He knows a lot more than I do, and can communicate quite well. I only know a smattering of words. I asked my grandmother (she grew up in Victoria) if she knew Chinook Jargon. She said no. I said ok, so you don't know what I mean if I say Klahowya Tillicum. She said.. oh, well yes, but that's just slang. I thought that was neat because it shows what it might have been like when it was still common enough to be taken for granted. I'd really like to become fluent. This language is our legacy as Pacific Northwesters. We should try to hang on to it.
My favourite Chinook Jargon site: http://tenaswawa.home.att.net/
It teaches the language by telling a story.. and there is even a song that you can download and listen to for a feel for how the language sounds spoken.