The San Clemente Island fox (Urocyon littoralis clementae) is a focal species for conservation by the U.S. Navy and has been monitored on San Clemente Island (SCI) almost continuously since 1988. We used mark-recapture techniques on trapping grids established in 2007 to examine patterns in annual variation of population size, growth, and density by habitat type. Between 2007 – 2020 the SCI fox population grew from an estimated 431 foxes in 2007 to 1,172 in 2020. The ratio of adult females to pups used to index reproduction varied from a low of 0.01 in 2007 to a high of 1.08 in 2017. Overall, the SCI population has steadily grown over the past 20 years. This increase may be related to vegetative recovery following the eradication of feral grazers in 1992 and efforts to reduce the feral cat population which are potential non-native competitors. The low reproductive indices in some years correspond with poor precipitation the preceding winter, and better understanding this relationship has implications for modeling how climate change could impact this population.