Assessing the spatial and temporal distributions of Northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) is critically important for managing these pelagic forage fish and understanding their roles in marine ecosystems. Here, we examined over 50 years (1963-2015) of larvae data collected across the southern California Current Ecosystem (CCE), focusing on the waters off of California and Mexico. Specifically, we asked where and when these fish larvae were found, whether their geographic distributions were linked to average larvae abundance, and whether or not the abundances of anchovy and sardine larvae were correlated in time. Larvae were found in some periods primarily in Mexico, California, or both—and in some cases with disjointed distributions—and these patterns were not consistent across species. During the period of extremely low sardine abundance in the U.S. in the 1960s-1990s, sardine larvae were still found in Mexico. We found that sardine and anchovy distributions expanded away from the coast when larval abundance were high for both species. Additionally, the correlation between anchovy and sardine larval abundance was highly dependent on spatial and temporal scale. By combining larval data across a broad section of this globally important coastal upwelling biome, we were able to explore questions regarding biogeography and phenology of these key species.