This article analyzes the recognition, development, and use of the power of persuasion in American sales letter from 1905-1920, as well as two other business-writing traditions which developed during this period: the “you” viewpoint and the five C's. Examples will show how these two traditions changed the language used in business letters, allowing these letters to play a dual role by making these letters easier for the consumer to read and understand and by using these letters to pursue the growth in national character of American business. The article concludes with a call for further research, to help prepare writers to produce the letters of the future.