best used record store s for "BLUES"?

Can anyone recommend a used record store for blues (in the US or Canada)? thanks.
bop street in Seattle. Dave, the owner, used to host a blues radio show
Don't know if it's the "best", but Princeton Record Exchange in Princeton, NJ, has a wide selection of used LP's. Here's the link to their web site:

If you are ever in Princeton, plan to spend a chunk of time browsing their inventory.