The mammalian cerebral cortex presents a modular organization, enabling the segregation of specialized functions and the generation of complex cognitive states. In the mouse, the anatomical and functional correlates of this network topology arise during the perinatal period. Especially after birth, spontaneous neural activity and sensory inputs trigger complex spatio-temporal firing patterns, which affect the cytoarchitecture and connectivity of cortical regions. Thus, understanding how local activity patterns emerge, interact and impinge on cortex-wide dynamics is essential to elucidate the proper development of the cortex. Here, we performed pan-hemispheric wide-field calcium imaging in Snap25-2A-GCaMP6s-D mice recording spontaneous and sensory evoked activity during the first two postnatal weeks. Through anatomical and functional segmentation, we then analyzed the spatio-temporal occurrence of cortical calcium dynamics. The results showed that while activity rates increased throughout the experimental time window, the spatial extent of calcium waves peaked at the end of the first postnatal week and then progressively decreased. Concomitantly, the predominant localization of calcium events shifted from medial to more posterior cortical areas. At the functional level, spatial domains arose already during the first postnatal days and their parcellation became finer later on. Around P9-10 the signal entropy plateaued and mesoscale connectivity was refined, such that information flows along canonical pathway of the mature cortex. In conclusion, our results indicate that wide-field calcium activity reflects the development of local electrophysiological patterns, and allows to infer critical steps of cortical functionalization on the mesoscale.Funded by a grant of the Deutsche Forschungsgemeinschaft (CRC1080 - Project A01).