Conservation planning and action critically relies on information about the dynamics in ecosystems, habitats, and species’ populations in order to define baselines, set conservation targets, and to identify areas for protection and restoration activities. Following the opening of the Landsat archives, remote sensing became a key technology for providing information to conservation, but many world regions experienced widespread changes in habitats and species populations prior to the Landsat history (1980s). In EcoSpy we pioneered the broad-scale use of recently declassified historical, global, high-resolution spy satellite photographs from the Cold War era (Corona) to extend the temporal scale of ecological and conservation remote sensing studies as far back as the 1960s. We integrated Corona with Landsat and Google Earth Images in three proof-of-concept studies to test the usability of Corona data for conservation research and applications. We assessed the changes in ecosystems of conservation concern, by identifying long-undisturbed forests in Romania, changes in human pressure on steppe ecosystems in Kazakhstan and changes in a keystone species’ population in the Kazakhs steppe. We also carried out a synthesis study on uses and benefits of Corona imagery for ecology and conservation worldwide. EcoSpy was a deeply interdisciplinary project, located at the intersection of ecology, conservation science and remote sensing. Scientifically, EcoSpy enhanced the long-term understanding of ecological processes such as land use legacies and time delayed effects and extended the use of high resolution remotely sensed data by two decades prior to Landsat. The main conclusion of the EcoSpy project is that historical remote sesing data can be a valualbe source of information on historical ecosystem states and for informing conservation practice in the pilot areas of Romania and Kazakhstan such as design of protected areas and promotion of sustainable land management practices.