DemographicsCastle Rock is approximately 91.15 square kilometres. In 2016 the population of Castle Rock was 175. The population is 52% male and 48% female. On average the monthly mortgage repayments in Castle Rock are $0 to $299. The most common weekly income bracket is $2000 to $2999 per week. Weekly rents in the area are on average $0 to $74.