Altadena, CA has a population of 45,001 and is the 912th largest city in the United States. The population density is 5,164 per sq mi which is 2122% higher than the California average and 5600% higher than the national average. The median age in Altadena is 43 which is approximately 20% higher than the California average of 36. In Altadena, 56% of the population over 15 years of age are married, 68% speak English and 20% speak Spanish. 54% of Altadena residents were born in California, 25% were born out of state, 1% were born outside of the United States and 20% were foreign born.