Actually, I believe the Capitol Tower was completed late in 1955. There is a publicity photo for Ernie Ford's release of "16 Tons" that featured Ford in uproarious laughter
posing as many tourists do with landmarks, holding their hand up so it looks like they're holding up the building. Ernie's doing this with the Capitol Tower, which still has a construction fence in front of it. It was completed later that fall.
Capitol Studios correction -- their NYC facility was definitely open by 1954
because a couple of the awesome Brown and Roach albums were made there for
Emarcy/Mercury. And they built their famous Capitol Tower studio in L.A. in
the early 60's.