Boston, MA has a population of 658,279 and is the 23rd largest city in the United States. The population density is 13,617 per sq mi which is 2063% higher than the Massachusetts average and 14929% higher than the national average. The median age in Boston is 32 which is approximately 20% lower than the Massachusetts average of 39. In Boston, 34% of the population over 15 years of age are married, 63% speak English and 17% speak Spanish. 44% of Boston residents were born in Massachusetts, 24% were born out of state, 4% were born outside of the United States and 28% were foreign born.