We present a reappraisal of Columbia River basalt petrogenesis based on an internally consistent X-ray fluorescence and inductively coupled plasma–mass spectrometry data set for major and trace elements plus new and existing isotopic analyses of the Imnaha, Steens, Picture Gorge, and Grande Ronde Basalts. Source materials for the main-phase Columbia River Basalt Group are upwelling ocean-island basalt source–like mantle, depleted mantle variably fluxed by slab-derived fluids, Phanerozoic arc crust, and ancient North American cratonic crust. The mantle upwelling may be a deep-seated plume or material displaced and mobilized by fragmented sinking slabs. We endorse the conclusions of earlier workers that...