This report is the result of a unique collaboration between a historian of astronomy and a historian of biology. As with the science itself, astrobiology history has fostered interdisciplinary cooperation and has led to insights that would have been unachievable if pursued alone. The history of astrobiology is presented in the context of NASA programs. Exobiology grew into a whole new scientific discipline by merging several previously quite disparate streams of research. Far from being a fluke or a short-lived creation that could only flourish under the relatively large infusion of money which NASA dispensed in the 1960s and 1970s for the Viking project, it has contributed significantly to viewing planetary scale processes such as global climate in a unified way. Exobiology actually favored interdisciplinary work that had great difficulty getting funded by the National Science Foundation (NSF) or the National Institutes of Health (NIH), the government agencies that fund most of the biological research in the United States. Since 1995 exobiology, under its new rubric of astrobiology, has expanded still further to embrace genomics, ecological research, and all science on the origin, history, and distribution of life in the universe. Today astrobiology remains a central driving force at NASA, a question of enduring popular interest, and one of the most important riddles of science. Given its fundamental questions, astrobiology is indeed here to stay.