There's nothing really conquering in their history or culture, though.
Maybe if some Europeans attempt to conquer the area very early on, but fail, due to handwavium (realistically I suppose supply lines were a problem, which I guess is why no Europeans tried to conquer the area until the mid-19th century).
So, have some, I don't know, Spanish/Mexican adventurer try and go up there in the 1600's with a ship or two and a handful of soldiers. They attack the first settlement they find, stealing some furs for themselves. However, the Spaniards find very little reason to stay and prepare to leave; during the night, they are attacked by two groups of Haida warriors; one on foot, one in canoes, to attack the ship. The surprise attack is a resounding success and most of the Spaniards are killed or captured, not having time to even reach for their weapons and not getting any support from the ship. However, enough Haida are killed in the fight that they recognize the potential of the European's weapons and armor; which they now have. In fact, the Haida have roughly 100 muskets and a fine (if small) Spanish galleon that, while running out of food, has plenty of gunpowder. In addition, they have captured enough of the soldiers that they receive training in how to use these technologies.
What I'm imagining is something like the New Zealanders' Musket Wars, albeit a bit earlier. Who knows, once they've set themselves up as a power (the Pacific Northwest is a pretty fertile region; if the Amerindians there put to use some European farming techniques, they could really make something of it; they already had a relatively urbanized society, one of the most so considering they were essentially hunter-gatherers).