Unequal park distribution threatens park access, especially in underserved communities as does a lack of recognition for users’ preferences. A lack of park access decreases the health benefits from parks available to communities. Thus, park access is an issue of Environmental Justice (EJ). EJ scholarship traces injustices to a lack of procedural justice which, I studied as public participation in decision-making about how parks look and operate. I asked the research questions, “How are park systems modified to better align with the public’s preferences?” and “What is the public’s role in driving those changes?” I drew on collaborative governance (CG) and social-ecological systems (SES) perspectives to understand the public’s role in park decision-making. I collected data in Minneapolis and Chicago. Both top the Trust for Public Land’s list of “best” city park systems and allow the public into decision-making to tailor park infrastructure and operation. I 1) reviewed plans and policy documents; 2) interviewed decision-makers including park supervisors, instructors, planners and administrative authorities, and public advisory councilors; 3) observed decision-making during daily park use, programs, and park board and advisory council meetings. Using the CG perspective, I found public and governmental collaboration in decision-making in four venues: board and advisory council meetings, programs, and daily park use. At times the public’s participatory preferences were incongruent to opportunities offered by government officials. Using the SES perspective, I found that park systems (parks and decision-making processes) were flexible. This allowed the public to address incongruence by modifying park systems using material and human resources, like knowledge of EJ. Participation in decision-making began to address procedural, recognition, and distributional justice by modifying existing, often-exclusive park systems.