Matthew Cobb has self-archived "The Prehistory of Biology Preprints: A Forgotten Experiment from the 1960s."
Here's an excerpt:
In 1961, the NIH began to circulate biological preprints in a forgotten experiment called the Information Exchange Groups (IEGs). This system eventually attracted over 3600 participants and saw the production of over 2,500 different documents, but by 1967 it was effectively shut down by journal publishers’ refusal to accept articles that had been circulated as preprints. This article charts the rise and fall of the IEGs and explores the parallels with the 1990s and the biomedical preprint movement of today.