S. H. Knox & Co. was a retail company based in Buffalo, New York, active from 1884 to 1911. Founded by Seymore Horrace Knox, the company entered into a partnership with his cousin Frank Woolworth to open the first five-and-dime store in Reading, Pennsylvania, in 1884. Knox expanded the chain, eventually becoming the second-largest in the United States and notably opening the first urban five-and-dime store in Detroit.
As the popularity of postcards grew, Knox became a significant distributor and publisher of postcards through his stores. In 1911, the company was merged into the F.W. Woolworth & Co. chain.