From the colonial period through the civil war period, naturalists in America were scattered over an extensive area, much of which was still sparsely settled, and all of which was very distant from the intellectual centers of Europe. Developing a network of contacts with like-minded naturalists took many years of correspondence. To facilitate communication among these naturalists, the Naturalists' Directory was compiled and first published in 1865. It has gone through more than 46 editions and is still being published. The role of the directory in the ever-changing communication process that has occurred in America from 1865 to the present is reviewed, as are the directories themselves: the early Frederic W. Putnam editions (which were published in association with the Proceedings of the Essex Institute, 1865-1866, the Samuel E. Cassino editions (editions 1-30, 1877-1936), and the post-Cassino editions (with various publishers, editions 31-46, 1938-1993).