If it doesn't have orange or red spots on it's flanks, and you found it in your area, it's a northwestern garter snake. I mean, if it doesn't look like this pic, then it's a northwestern. (Thamnophis ordinoides).

Oregon Red Spotted: (Thamnophis sirtalis concinnus)



Some Northwestern garter snakes:



I can't seem to find the thread that tells you how to post pics. Anyone else know where it is?