Network building vitally impacts career development, but in few professions does it impact daily practice more than in teaching. Teacher networks, known as professional learning communities, communities of practice, peer learning circles, virtual professional communities, as well as other names, play a unique and powerful role in education. In addition to providing opportunities for teachers to impact school change on local, state and national levels, networking links teachers directly to resources that improve classroom environments and support the generation of instructional tools, which directly impacts student learning. The diverse and vast knowledge base of networks includes school-wide, grade-level, and content area strategies. It also includes innumerable approaches to learning, such as project-based learning, connected learning, and maker-centered learning. Leveraging this knowledge base through a network brings novice teachers into the fold, supports the professional growth of mid-career educators, and reinvigorates seasoned veterans. Teacher networks present opportunities for teachers to serve as peer mentors, rediscover intellectual passions, present and discover new models of learning, and reframe their professional identities as teacher-researchers, teacher-leaders, and teacher-mentors. For these reasons, the Philadelphia Education Fund (Ed Fund) has incubated and advocated for teacher networks through program and policy efforts for more than two decades. The Ed Fund's investment in teacher networks is a critical piece to impacting Philadelphia's teacher network landscape through District-wide policy initiatives, teacher network-based professional development, teacher convenings, and teacher pipelines.