William Deas (1768-1806) was a merchant in Philadelphia, Pennsylvania. Initially, Deas was in a partnership with David Knox (dates unknown) and James Henderson (1756-1801) Knox, Henderson, and Co., which formed in 1796. After that partnership was dissolved, William Deas and David Knox formed a new partnership, Knox and Deas, located at 30 Front Street in Philadelphia. The business imported and sold textiles and garment-making items as well as dry goods and other things. This collection consists of a letterbook of approximately 175 pages of business transactions from William Deas to his business partner, English merchant David Knox, from 1800 to 1803 inclusively.