The transformation of an abandoned elevated rail line into an urban linear park in New York City helped catalyze urban greening projects that imaginatively re-use urban space in other cities. Chicago and Philadelphia offer examples of these new types of small-scale urban greening in the revitalization of marginal and post-industrial land. Drawing on interviews with key stakeholders involved with the projects, policy goals, and analysis of media coverage, the chapter looks at the policies, people, and research that enabled the programs, and at key successes, challenges, and lessons learned for each project. Specifically, the chapter examines policies to invest in disadvantaged communities through the revitalization of vacant land and post-industrial railway corridors – the Rail Park in Philadelphia and The 606 in Chicago – as new public greenspace. Key insights include the recognition of these projects as both social and ecological, the role that research plays in both supporting these projects and policies and challenging them, and conflicts around these projects as agents of gentrification and displacement. The chapter concludes with a discussion of the potential positive role of marginal land, particularly as a place for free play and non-consumerist spaces, biodiversity, and learning.