At Harvard Asa Gray established academic instruction during the summer and in so doing he opened facilities to an audience that included not only Harvard College students but also teachers and professionals from across North America. The Summer School of Botany established in 1871 spawned the Summer Schools of Natural History, of Chemistry, and of Geology. His summer school and all subsequent offerings included women. This article places Gray's summer school in the context of his efforts to build botany at Harvard but also documents his influence on instruction and curriculum development.