We assessed the current status and potential future development of the only Atlantic white-cedar (Chamaecyparis thyoides) population in Pennsylvania (Spruce Flats Bog in Westmoreland County). We counted all stems in the population and measured the diameter at breast height of all stems ≥ 1.4 m in height. Increment cores were collected and analyzed from 93 trees to quantify age distribution. We also evaluated relationships among cedar regeneration, microtopography, and other potentially competitive vegetation. Potential recruitment from the seed bank was assessed via the germination method using soil samples from 46 hummocks in the bog. The population consisted of 395 stems with stem size structure characterized by an “inverse-J” distribution; most stems (67%) were < 1.4 m in height. The oldest individuals were established in the 1940s, but recruitment has been steady since initial establishment. Hummock area and mean height above the water table were positively related to the abundance of C. thyoides. No C. thyoides seeds germinated from soil samples during a 14-month period, indicating that the bog's seed bank may have limited potential to contribute to recruitment. We suggest that this population has naturalized from plantings in the 1940s, with most recent recruitment having been vegetative. Because of previous extirpation of C. thyoides from Pennsylvania wetlands, the naturalization of this population has conservation value. Although the population size is probably limited by the number of microsites sufficiently high above the water table to avoid excessive inundation, direct management of this population does not currently appear to be necessary in order to ensure its continued survival.