Thanks. Yes, it was built for Eastern. But
@RandomWalk 's comment got me thinking: I knew it was still in use between the early-90s when Eastern folded and the early-aughts when it was demo'd, but only vaguely remembered who was in there. Then I remembered flying Continental out of there at least once in that timeframe - thanks for corroborating. Forgot about USAir.
I have fond childhood memories of Terminal A from when my dad and I used to pick up an aunt from the DC area who used to fly in to visit on Eastern a few times in the late-80s. It was a totally different era when you used to hang out in terminals to meet people.