Anybody know at what point in time the individual key width of the piano became standardized to the modern width?? Thanks!

Take a look at this history lesson: http://www.uk-piano.org/history/compass.html

The piano's compass is still not fully standardized. American pianos tend to have the shortest compass and European pianos the longest. The differences are less than an inch.

I think it has been more or less standard
from the earliest times, since the size
of the ends of people's fingers has not
changed. For example, I saw an ancient
organ on tv and the rough-hewn wooden
keys looked the same size as on a modern piano.
A modern piano player would thus have no
problem playing any keyboard instrument
from any era.

Pianists with smaller hands can get 7/8s keyboards (designed for Steinway B & D)to slip in instead of the original.

You will find some varying sizes on harpsichords.

It is said that Mason and Hamlin widened their sharps to discourage jazz playing on their pianos (for a time).

Great history link Jim!

If I recall correctly, which I may not be, classic American pianos had a compass of about 42 7/8", European pianos about 43 1/2, with Japanese pianos in between.