This paper addresses the function of neural stem cells in the mammalian brain, and how these cells are generated and maintained. As the Wnt signaling pathway is crucial for development of the central nervous system, we examined the role of Wnt signaling during neural stem cell maintenance and differentiation. We were able to label neural stem cells using a recently developed mouse strain and thereby follow the developmental fate of Wnt-responsive cells in both the embryonic and postnatal mouse brain. From as early as embryonic day 8.5 onwards, we found neural stem cells being labeled in functionally restricted populations. Labeling in the postnatal brain demonstrated the persistence of long-lived, Wnt responsive stem cells in both of these sites. These results demonstrate the continued importance of Wnt signaling for neural stem and progenitor cell formation and function throughout developmental time and have implications for cancer from this tissue as well.