This paper critically engages the uneven distribution of infrastructure provision, connectivity, and mobility in contemporary neoliberal urban landscapes by uncovering the path dependent trajectories and politics of transportation in post-suburbia. Departing from contemporary debates on the evolving geography of urban peripheries, I utilize a relational theorization of the ‘in-between city’ to empirically unpack the urbanization processes internalized in the evolution of the ‘Zwischenstadt’ in a North American context. Through a longue durée case study of transportation planning, politics, and spatial practice in Chicago’s ‘Crosstown Corridor’, in-between urbanization is demonstrated to express an on-going multiscalar mediation of co-habiting modes of urbanism and strategic state actions that challenge generalized (sub)urbanization narratives. Despite continued interest from planners, politicians, and business groups, proposals for both a major urban expressway and rapid transit line have proved political lightning rods. Consequently, neighborhood protests, personal political battles, and macro-economic trends have locked-in a neglected development pathway for Chicago’s inner suburbs. I argue that through disclosing key contradictory political-economic imperatives and conflicting scales of mobility, it is possible to identify space for political and planning interventions that can adapt to, and develop, polycentric urban practice in and through in-between urban space.