Mountain Brook, AL has a population of 20,532 and is the 2,114th largest city in the United States. The population density is 1,601 per sq mi which is 1640% higher than the Alabama average and 1667% higher than the national average. The median age in Mountain Brook is 41 which is approximately 5% higher than the Alabama average of 39. In Mountain Brook, 77% of the population over 15 years of age are married, 96% speak English and 1% speak Spanish. 66% of Mountain Brook residents were born in Alabama, 31% were born out of state, 1% were born outside of the United States and 2% were foreign born.