In the year 1876, the first World's Fair outside of Europe took place. That event happened in Philadelphia and it corresponded with the Centennial of the USA.
It was also a time that America was able to show Europe that we no longer needed to import fine things and the Centennial Grand by Steinway was a prime example of that. In fact, it won a competition there that included many of the world's finest pianos at the time. This was the first model of concert grand that had 88 notes and had a sostenuto pedal. It is today considered by many to be the world's first modern piano.
This Centennial is #123 out of a total of 424 that were built.