Coquimbo has been Chile's fastest growing region in economic and population terms in the past four decades, even more than Antofagasta-the mining capital-and the Metropolitan Region, thus becoming a regional paradigm in our country. Not free from contradictions, the epicenter of its dynamism is the La Serena/Coquimbo conurbation, about to become the first metropolitan area of the country's north. This involves true challenges in terms of efficiency, equity and sustainability for urban planning and design. This article offers a comparative analysis of the two fastest growing quasi-metropolis in Chile, La Serena/Coquimbo and Antofagasta, considering their economic and demographic bases, labor markets and persistent extreme poverty and poverty levels. Unquestionably, the transition of both cities-linked to mining and with similar quantitative growing indicators but contradicting development processes-from mid-size to metropolis is a strategic planning, governance and urban design opportunity.