Curriculum-based professional learning is situated within the broader professional learning ecosystem. It focuses on how to teach a specific subject for specific grades, using the specific materials that teachers will use with their students. Given the potential of curriculum-based professional learning to support teachers and strengthen educational experiences and outcomes for students, Columbia University's Center for Public Research and Leadership recently conducted a study to explore the state of the field of curriculum-based professional learning and how it might grow to give all teachers rich professional learning. The research revealed the field of curriculum-based professional learning is in its early, or emerging, stage. Yet this emerging field shows great promise. A diverse set of stakeholders -- including funders, system- and state-level leaders, a growing number of professional learning providers, teachers and leaders, and many others -- are aligned on a number of key approaches to promoting teacher effectiveness through curriculum-based professional learning. The infrastructure supporting these stakeholders is forming, with many linked through networks, associations, and shared knowledge and tools. Individually and collectively, stakeholders use a limited but growing knowledge base about curriculum-based professional learning to inform their practice, and they access limited but increasing public and private dollars to support implementation. The research surfaced a set of recommendations, which conclude the article, about how to move the field from an early to middle stage, ensuring more teachers get the support they deserve.