The 2014 Portland, Maine, population is 66,235. There are 3,108 people per square mile (population density). The median age is 36.7. The US median is 37.2. 38.53% of people in Portland, Maine, are married. 13.81% are divorced. The average household size is 2.08 people. 27.60% of people are married, with children. 19.64% have children, but are single.