What Happened to the Spin Crisis in High Energy Physics?

Twenty years ago the European Muon Collaboration (EMC) surprised the high-energy world with data that implied the spin of the proton is mostly carried by gluons and not the valence quarks. This resulted in a spate of activity to explain the apparent disagreement of theory and experiment. This paper reviews the theoretical and experimental developments since then to shed light on the spin structure of the proton and neutron. Future plans for extending this to heavier baryons will be discussed.