He was an advocate of international copyright reform, secretary for many years of the Publishers' Association, and founding superintendent of the Metropolitan Museum of Art.

In 1848, he returned to New York City, where he dissolved the partnership with John Wiley and established G. Putnam Broadway, publishing a variety of works including quality illustrated books.

[2] His company was the official publisher to the New York World's Fair in 1852.. Putnam published the books of many classic American authors including his close friend Washington Irving, William Cullen Bryant, James Fenimore Cooper, and Edgar Allan Poe.

He is believed to have been the first publisher to offer book royalties to authors, including Elizabeth Barrett Browning and Thomas Carlyle.

George Palmer Putnam's grandson and namesake, George P. Putnam (1887–1950), was part of the family business but was also an author and explorer whose first wife was Dorothy Binney, the daughter of Edwin Binney who founded Crayola; after their divorce, he married the famous aviator Amelia Earhart.