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The geological record at rifts and margins worldwide often reveals considerable along‐strike variations in volumes of extruded and intruded igneous rocks. These variations may be the result of asthenospheric heterogeneity, variations in rate, and timing of extension; alternatively, preexisting plate architecture and/or the evolving kinematics of extension during breakup may exert first‐order control on magmatism. The Main Ethiopian Rift (MER) in East Africa provides an excellent opportunity to address this dichotomy: it exposes, along strike, several sectors of asynchronous rift development from continental rifting in the south to incipient oceanic spreading in the north. Here we perform studies of volcanic cone density and rift obliquity along strike in the MER. By synthesizing these new data in light of existing geophysical, geochemical, and petrological constraints on magma generation and emplacement, we are able …