This report is an evaluation of efforts made by Illinois Action for Children (IAFC), with oversight from the Illinois Governor's Office for Early Childhood Development (OECD), to test, support, and facilitate innovations in the early childhood system in 11 communities across the state. The Early Childhood Innovation Zones (IZ) initiative, funded by Illinois' Race to the Top--Early Learning Challenge (RttT-ELC) grant, was designed to spur experimentation with new systemic strategies for increasing the number of children from priority populations enrolled in high quality early learning programs. This mixed methods study is designed to help further the state's understanding of the functioning of the project's logic model and describe the relationships between stages in the theory of action. The analyses focus on identifying and describing the supports, capacities, strategies, and outcomes observed within each collaborative, as well as across collaboratives. The analyses utilized the following: (1) qualitative data, including interviews with zone partners and state level program staff; (2) project documentation, along with quantitative data on enrollment and quality collected by each zone; and (3) surveys distributed to all program participants. The first section addresses innovations in capacity-building, technical assistance and other supports facilitated by IAFC, and describes the problem-solving and decision-making strategies introduced to the zones, as well as the obstacles to implementing the project framework. The second section provides information about barriers to enrollment in early learning programs, and an in-depth exploration of the strategies zones used to overcome these barriers and increase enrollment of priority populations. The third section of this report describes innovations for improving quality implemented by the four zones that chose this path. The report concludes with a discussion of key lessons learned and questions arising from this study, along with implications for future policymaking efforts. The following are appended: (1) Innovation Zone Interview Protocol; (2) IAFC Interview Protocol; (3) Innovation Zones Interview Coding Schema; (4) Innovation Zones End-of-Grant Survey; and (5) Appendix Tables 1 and 2. [For the executive summary, "Illinois' Early Childhood Innovation Zones: A New Model for State Policy? IERC 2017-1. Executive Summary," see ED574336. For the research highlights, "Illinois' Early Childhood Innovation Zones: A New Model for State Policy? IERC 2017-1. Research Highlights," see ED574339.]