The two most significant publications in the history of rockets and jet propulsion are "A Method of Reaching Extreme Altitudes," published in 1919, and "Liquid-Propellant Rocket Development," published in 1936. All modern jet propulsion and rocket engineering are based upon these two famous reports. By arrangement with the estate of Dr. Robert H. Goddard and the Smithsonian Institution, the American Rocket Society republished the papers in 1946. The book contained a foreword written by Dr. Goddard just four months prior to his death on 10 August 1945. The book has been out of print for decades. Because of the importance of the Goddard papers, the American Institute of Aeronautics and Astronautics is pleased to bring this significant book back into circulation. Though rockets had been in use for more than 700 years, it was not until Goddard undertook his lifelong work on the development of high altitude rockets that modern scientific and engineering methods began to be applied. These reports form one of the most important technical contributions of our time.