size of mercer county population
Population of Mercer County. Last official estimated population of Mercer County was 368,043 (year 2014)[1]. This was 0.115% of total US population and 4.1% of total New Jersey state population. Area of Mercer County is 228.9 miÂ² (=592.8 kmÂ²), in this year population density was 1,607.96 p/miÂ².