I'm new to SW Washington state-I saw a snake....?

Question

...yesterday, and it was a beauty. It was about a foot-and-a-half long, shiny black, and had a single, bright red stripe running down the middle of its back. At first glance I thought it might have been a garter, but it seemed to be darker and had the red stripe instead of the two yellow ones. What kind of snake was this?

Answer 1

Could be a Northwestern Garter - I've never seen that one, but I understand some color morphs have a red stripe instead of a yellow one down the middle.

Answer 2

Perhaps it could be a red back snake. We have red back spiders here