Atherton, CA has a population of 7,127 and is the 5,121st largest city in the United States. The population density is 1,417 per sq mi which is 510% higher than the California average and 1464% higher than the national average. The median age in Atherton is 48 which is approximately 33% higher than the California average of 36. In Atherton, 65% of the population over 15 years of age are married, 82% speak English and 3% speak Spanish. 45% of Atherton residents were born in California, 36% were born out of state, 1% were born outside of the United States and 18% were foreign born.