I know this can vary and it's a rough estimate but I thought I'd ask anyways.

My girlfriend and I are considering flying from Canada to attend and I'm wondering how many people roughly attended last year?

Are we talking like <10 people and it's a small board game night or is it 100+ where it's basically a mini convention or something like 20-40 people which is tournament size.

Every year I've gone it's been at least mini convention size. If not, just under.

Last year was somewhere between tournament and mini convention size, I'd say. 70ish? It was pretty great. Enough people to always have games going, few enough that there's plenty of swag to go around. Come join us in Southern Canada!

Last year was a pretty good crowd. I would concur with the above posters in around ~70 players. No problem finding a group to play your favorite Arkham themed game. It's been fun every year I have gone.