The Great Chicago Fire of October 1871 destroyed the neighborhood where the P&C stands today. One of the principal residents of the neighborhood, George Dunlap, who sold land to William Waller in 1874 on which the current building was erected, was burned out in the fire. But Dunlap vowed to rebuild. Here is an item from the Chicago Tribune of April 1872:

As of May 1875, however, Dunlap had not rebuilt his home. We know that from the following Tribune article, noting that Dunlap had engaged architects for that purpose:

I have a photograph of the Dunlap home that I will be posting here soon. It matches this 1875 description perfectly.

What this means is that the Waller home–the P&C’s current home–was built before the Dunlap’s.