The special issue (SI) is comprised of 11 articles describing the history of the International Union of Geodesy and Geophysics (IUGG) and its eight International Associations. The SI is dedicated to the centennial anniversary of the Union, which has been coordinating and promoting international efforts in Earth and space sciences since 1919.
The purpose of this SI is not to relay a definitive history of the development of international cooperation in geosciences, but to summarize IUGG's remarkable role during the 100-year span of its existence. The first three articles present the history of IUGG from its founding through the years of extraordinary development of geophysical sciences and the concurrent evolution of the Union's structure and programs extending up to its advances at the beginning of the 21st century. Outstanding histories of each of the IUGG Associations are then presented.