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Many reptile species are in decline and turtles are especially susceptible. In Massachusetts, eastern box turtle (Terrapene carolina carolina) population densities are critically low, and they are listed as a Species of Special Concern. To aid in the conservation of this species, we developed a statewide population monitoring program to track large-scale population trends. We used GENPRES3 to identify the most efficient sampling design a priori. Using this design, we performed visual surveys in 2010-2012 and used site occupancy models to evaluate baseline occupancy and abundance data. We surveyed 62 4-ha monitoring plots within early successional and forest edge habitat where box turtles congregate in the spring for foraging, mating, nesting, and thermoregulation. We also used radio-telemetry at 2 survey sites to evaluate assumptions and further assess occupancy rates, detection estimates, and population size. The best fit Royle-Nichols model predicted a probability of box turtle occupancy of 0.81 +/- 0.10 (mean +/- SE) and a mean probability of detection of 0.29 +/- 0.18. Roads and vegetation density were important covariates affecting the probability of occurrence. Survey start time, humidity, and surveyor were important covariates affecting detection probability. A power analysis indicated that we could detect a 10% decline in occupancy between 5-year sampling rounds within 15 years. The proportion of radio-tagged turtles inside the survey plots during surveys was relatively constant at each site (0.44-0.63 and 0.36-0.43), mean detection rate was 0.35 +/- 0.10, and the total estimated population size of the 2 survey plots (8 ha total) was 13.31 +/- 1.53. Our results can be used to track the status of this rare species as well as guide conservation actions and evaluate the effectiveness of site-specific and statewide management plans. Our approach and design can serve as a model for other states developing monitoring programs for the eastern box turtle and other similar, rare and difficult to detect species. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.