Cousineau, S.M. JACoW Publishing Geneva, Switzerland Since it’s emergence in the first half of the twentieth century, the field of accelerator science has supported an active and expanding R&D program leading to many advances in accelerator capability. This has resulted in extraordinary scientific discoveries in nuclear physics, particle physics, materials science, and related fields. Through a series of case examples, this talk will highlight the relationship between scientific accomplishment and the enabling transformative accelerator R&D, both historically and in recent years. It will provide a perspective on common trends and timescales for accelerator R&D, and will discuss accelerator R&D as a driver for both planned and unplanned scientific discovery.