original blueprints?

i'm wondering if there's any way to track down the original layout of the apartment i live in. it's on 7th ave between union and berkeley in a 4 story building with a business on the bottom and 3 apartments above.

i suspect it was originally 6 apartments, but im not sure, and i'm really curious about how it was laid out when it was built.

any idea where i could look for blueprints or architectural records?

thanks!