Astrocytes constitute a heterogeneous population of cells in terms of function and morphology. Although several embryonic sources of cortical astrocytes have been reported, cortical progenitors located from the dorsal pallium are considered their main production site. However, the potential link between the heterogeneity of cortical astrocytes and their developmental origin remains elusive. Recently, we identified a new embryonic source for cortical protoplasmic astrocytes located outside of the dorsal pallium, in a restricted domain containing Aldh1L1-expressing cells. In order to further characterize this source, we used Aldh1L1-CreERT2 and MAGIC Markers multicolor reporter mice to mark these precocious Aldh1L1-progenitors and to track their cortical descent from early to late developmental stages (E13.5-P60). Using in situ hybridization, immunostainings, cell quantification and 3D morphological reconstructions of Aldh1L1 progenitors and cortical astrocytes on brain slices, we found that Aldh1L1-expressing domain extends ventrally from the pallial-subpallial boundary in the lateral ganglionic eminence (LGE) to the medial ganglionic eminence (MGE). It produces cortical astrocytes with protoplasmic-like morphologies that colonize the cerebral cortex via an unusual migration pathway and are distributed in all cortical areas and layers with a preferential location in prefrontal regions of the adult mouse brain. In conclusion, we discovered another embryonic source for cortical astrocytes within a complex Aldh1L1-expressing domain that is located outside of the dorsal pallium. Our findings highlight the diversity of cortical astrocyte origins during brain development and raise questions about the link between these distinct developmental sources for cortical astrocytes and their respective contributions to specific brain functions or pathologies.