Solid and resilient democracies rest upon an informed citizenry capable of critiquing societal issues and reimagining alternative scenarios. Traditional school-based civic and social justice education, however, often falls short of addressing the diverse needs of today's youth, often relying on instructionist pedagogies focused on factual knowledge and standardized assessments related to government and electoral issues. On one side of the civic education spectrum, approaches rooted in the Critical Pedagogy movements of the 1970s reemerge, claiming an education rooted in a structured critique of today's social dilemmas. On another side of the spectrum, emerging scholarship -- often called "new civics" -- emphasizes the importance of additional skills, literacies, and dispositions for youth to engage with complex social issues and envision potential solutions critically. Speculative and utopian pedagogies, two of such new approaches to civic and social justice learning, invite students to elaborate diverse and even multiversal scenarios as alternatives to current situations of oppression and inequality. But to what extent are such imagination-driven pedagogies solid and robust to promote learning based on a well-thought critique of modern society? One of the central questions this dissertation sought to answer is how educators working under a speculative civics' paradigm might reconcile criticality and imagination in their programs. How might we design mechanisms and processes in a learning environment that are imaginative enough to go beyond the constraints of reality while sufficiently grounded on the vicissitudes of one's lived experience? To answer these questions, this dissertation adopted a Design-based Research Approach (DBR) in which a civic imagination workshop was designed and refined in consecutive iterations. For this task, adolescents of two marginalized groups were recruited in two distinct countries: the United States (where participants were recruited in the city of Santa Ana, California) and Brazil (where participants were recruited in Rocinha, a favela in the heart of Rio de Janeiro). After four iterations -- described in this study as thick design narratives -- this study found several building blocks and design principles for promoting critical civic imagination and civic identity: 1) decoding and recoding, 2) back-and-forth design, and 3) civic storytelling. The study also identified critical dark patterns -- undesired and unplanned processes that might emerge among the youth participating in civic imagination workshops. Finally, this dissertation ends with a discussion about the implication of the findings for designing interventions under a new civics' paradigm, especially those seeking to blend harsh critique of social dilemmas and speculative thought about potential worlds that are creative, imaginative, and attainable. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]