I saw Emmylou Harris (with Buddy Miller on guitar) at the same Borders. It was very crowded. I think her daughter was actually an employee and local college student at the time. Or something like that.
The saddest instore I saw in DC was when Alejandro Escovedo played DCCD in front of me, a friend, and the store clerks. And I wasn't really even a fan. Not sure why nobody turned out, it was before he managed to parlay the media attention to his illness into a surge in popularity (sounds mean to say that, but it did seem that way...I'm sure some would argue he had a burst of creative inspiration following his illness).
I want to say I saw Steve Earle and Del Mcoury at the Borders or whatever on 19th street that recenty closed..this would have been around 1999