Where is Paddy's Irish Pub?

so I like It's Always Sunny in Philadelphia, that TV show on FX. It's pretty hilarious. Something I've been wondering, however, was where their bar, Paddy's Pub, is located - is it a soundstage? Some place in Philly? LA? I dunno. The best I've found so far was a Philadelphia Weekly blog post from 2005 mentioning the show briefly. Turns out they aren't the best predictors:

Rumors were swirling that an FX network TV pilot called It's Always Sunny in Philadelphia was being shot on Ninth Street last weekend, and when we did a little investigation, we discovered the rumors were true. The comedy sounds like a pale Cheers imitation, undoubtedly with bad Philly accents and more stereotypes than an article about cheesesteaks. The plot revolves around a group of friends who own a Philly bar, one of whom reveals he has cancer in the first episode. We can't wait to see where they're going with this one. Then again, maybe we can.

FX=trying OUT a new comedy series is a risky proposition!

Philly=always desperate for OUT-of-towners' approval!

So, 9th Street. And supposedly it's in South Philly. That's all I got. From one of the shows, it looks like there's a parking lot down the street from the bar.

Anyone else have an idea?