The study of neutrino oscillations has evolved from the generation of anomalies, the solar and atmospheric neutrino problems, into a precision science, driven largely by long-baseline (LBL) accelerator-based experiments. We trace this evolution, beginning with the definitive evidence for neutrino mass from atmospheric and solar neutrino experiments, which motivated the need for controlled, man-made neutrino sources. We review the progression through three generations of LBL experiments, highlighting key results from K2K, MINOS and OPERA, and the currently operating T2K and \nova\ experiments. A pivotal moment in the field, the discovery of the relatively large value for the mixing angle $\theta_{13}$, is discussed, as it reshaped the global strategy for addressing the remaining fundamental questions: the neutrino mass ordering, the octant of $\theta_{23}$, and the existence of leptonic CP violation. The recent results from the joint analysis of T2K and \nova\ data, provide tantalizing hints but leave these questions open. Finally, we look to the future, outlining the immense scientific potential of the next-generation experiments, Hyper-Kamiokande and DUNE, which promise not only to resolve the remaining questions in the three-flavor paradigm but also to conduct sensitive searches for proton decay and provide unprecedented views of astrophysical phenomena like supernova bursts.
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