An alternate spread of crops and alternate founding of trade routes throughout North America help native tribes in the Pacific Northwest build a more advanced civilization than in OTL. Its early centre is in the Willamette Valley in OTL modern day Oregon.
The TL has two incarnations:
1.) The original, MkI version, which is now abandoned and which you can read here.
2.) The current, ongoing MkII version, which you can read here.