The Classic period Puuc region presents Maya archaeologists with significant challenges. One challenge to interpretation lies in the fact that, despite a form of agro-urban settlement that proved highly resilient in the Maya Lowlands overall, Puuc cities flourished relatively briefly, beginning on a grand scale in the sixth century C.E. and with a halt in major building construction and depopulation in the tenth century C.E. This chapter focuses on analyzing how the Puuc economy depended on sustained economic growth and ultimately suffered its consequences for long-term agro-ecological sustainability. We suggest that an important clue to understanding urban collapse in the Puuc is found by looking at transitions in the net energy gain of the agricultural economy over the longterm. The boom-and-crash character of Puuc economic history follows a series of opportunities, challenges, and problem-solving with varying efficacy for long-and short-term sustainability and resilience. These factors include the highly fertile soils as the main resource; water scarcity as a limiting factor; effective water management as a key solution; and costly social complexity a driving force of agro-economic growth. The diminishing returns on energy invested were consequences of a dependency on economic growth as the supply of the primary resource decreased. The elite segments of polities were unable to adjust to decreasing returns, which led to economic decline and, eventually, organizational collapse. The boom-and-crash character of Puuc settlement suggests a political economy that had locked into dependency on constant growth and failed to adapt to diminishing returns. [Puuc Maya, political economy, agro-ecological sustainability, growth, decline]