In a joint venture with Harry Weese Associates, BNIM won a national design competition sponsored by the General Services Administration to renovate the St. Louis Old Post Office built in 1884. More than 650 federal employees occupy flexible office areas on the upper four floors, with commercial space available in the sub-basement, basement, and first level for shops, restaurants, and display areas.

The restoration of an existing second floor skylight subtly separates the commercial activity below from the government functions above. Removing central areas of the first and basement floors and creating a new central staircase, which opens onto the unusual double atrium, provided accessibility to the lower floors.

Since the renovation was a sensitive public issue, BNIM's design philosophy for the building stipulated minimal intervention upon the original character and integrity of the building. The Old Post Office's design has become a focal point for pedestrian traffic while contributing to the rejuvenation of downtown St. Louis.