Setting the Cornerstone, Building 21
President William L. McKnight, accompanied by chief engineer E. M. Johnson, supervised the installation of the cornerstone in October 1939.
The mason worked for the William Murphy and Son Construction Company. The date had been carved before the stone was set.
Etching the Cornerstone, Building 42
The Building 42 cornerstone contained a time capsule holding samples of 3M products, the 1949 company annual report, a copy of Megaphone magazine, a history of the company, newspaper accounts of the attempted assassination of President Harry S. Truman several days earlier, and an aerial photo of the Saint Paul Plant.