The public mandate to engage the public in transportation planning processes is in the process of becoming more rigorous and democratic. Transportation agencies are recognizing the limitations of past modes of engagement and seek to connect more dynamically with the public, particularly with historically marginalized communities. Doing this work well is a topic of interest to a growing number of transportation professionals. This study identified four successful engagement processes with historically marginalized communities in California by surveying transportation professionals. Stakeholders at each site were interviewed and public documents from the processes were reviewed to identify common themes for positive public inclusion. Interviewees included community leaders, transportation staff, and consultants. Interviews were coded and analysis was conducted using a mobility justice and critical race studies framework. Ten key themes of successful community engagement with historically marginalized communities were identified. These themes are: (1) trust is crucial; (2) treat community-based organizations as equal partners; (3) pay community partners fairly; (3) let community-based organizations decide what good community engagement is; (5) translate technical jargon; (6) engage in community concerns beyond the scope of the project; (7) address major community concerns such as displacement, policing, and youth development; (8) know local histories of transportation injustice; (9) include the community in the final reporting process; and (10) follow-up on planning with implementation in a timely manner.