Published by the American Geophysical Union as part of the History of Geophysics Series, Volume 7. The beginnings of magnetospheric physics were the beginnings of space physics, of the marvelous discoveries made from in situ measurements from rockets and satellites and from increasingly sophisticated ground-based measurements and computer-assisted theoretical and empirical research. The beginnings of magnetospheric physics are also intimately connected with the International Geophysical Year 1957-58, the greatest world-wide cooperative scientific event in history. From the period following World War II until the late 1960s, the United States, and world physics and engineering in general, entered a new level of large-scale research epitomized by "space physics." Covering the period roughly 1958-1967, this volume contains personal accounts from those pioneers whose pathfinding research initiated and solidified the field of magnetospheric physics. Here are accounts of the first rocket and satellite studies, of the discovery of the magnetosphere and Van Allen belts, of early models of the physics of the space around our Earth and of the Earth's environment within the Sun's plasma. Studies of the magnetosphere of the Earth led directly to our knowledge of the plasma environment around other planets and throughout our solar system. The authors of papers in this volume were in at the beginning, pioneers who played a significant role in the early years of magnetospheric physics.