Frank Kennicott Reilly (19 March 1863 – 25 May 1932) was one of the founding partners of Reilly & Britton, the publisher of the majority of the literary works of L. Frank Baum and thirteen of his fourteen Oz books.
Frank K. Reilly was from a medical family. His father, Frank W. Reilly, was a physician, public health reformer, and assistant health commissioner of Chicago from 1895 to his death in 1909 — and also a journalist and for a time the managing editor of the Chicago Morning News. Frank K. Reilly's mother was Alice May Kennicott, daughter of Dr. John A. Kennicott. Frank K. was the eldest of their three sons; his younger brother Leigh Reilly became a newspaperman, rising to managing editor of the Chicago Herald and the Chicago Evening Post.
Frank K. Reilly began his business career with various firms; he became a deputy manager for a Chicago publisher, Werner Co., in 1894. In the early twentieth century Reilly was the production manager of the George M. Hill Company, the firm that published the first edition of The Wonderful Wizard of Oz (1900). When the Hill company went bankrupt in 1902, Reilly joined with sales manager Sumner Charles Britton to form Reilly & Britton. Reilly was secretary and treasurer of the company from 1904 to 1913, and president from 1913 until his death.
Both with the Hill company and with his own firm, Reilly had a knack for promotion, what he called "stunts — the best sort of advertising, free publicity in the newspapers...." For the Oz books, he ran contests and a fan club, and staged Oz playlets with child actors in department stores. (On the subject of Oz promotion, see A Day in Oz and Promotional merchandise.)
Frank Reilly remained active as president of the publishing company until his death from heart disease in 1932.