Here, to enable researchers to more fully harness the collective discovery potential of multiomic data in the public domain, we have assembled gene-level transcriptomic data from ~200 studies of neocortical development and in vitro models. Applying joint matrix decomposition to mouse, macaque and human data, we define transcriptome dynamics that are conserved across neocortical neurogenesis and identify a program that emerges in ventricular progenitors, is later expressed in neurogenic outer, or