I'm sure there are a lot of people here from San Francisco so I'm going to assume some(a lot hopefully!) of them have had this before.
The Buena Vista Cafe in San Francisco is credited with inventing the original Irish Coffee. I assume this is true since I have haven't come across a lot of info that says otherwise :D
Regardless of whether or not you believe they invented, I assure you this - It's a damn good Irish Coffee! Well worth the trip there for anyone ever visiting San Francisco. A little bit touristy yes, but I don't really care... the coffee was good!
Here is a link to the place from Tripadvisor