My house was built in 1821 (or possibly earlier, but 1821 is what I can
document). It's post and beam with 3x7 and 2x7 "studs" filling between the
posts. Spacing ranges from 14" oc to 16"oc for the walls, floor joists are about
the same and tending to be more in the range of 16" oc. And, yes, I know that
the wall studs aren't structural, they're there to hang the lathe (accordion)
for the horsehair plaster.

DGW

> I would be really interested to know the oldest example of uniform 16" 
> spacing.