Plymouth, MI has a population of 8,956 and is the 4,280th largest city in the United States. The population density is 4,048 per sq mi which is 3913% higher than the Michigan average and 4368% higher than the national average. The median age in Plymouth is 40 which is approximately 2% higher than the Michigan average of 40. In Plymouth, 57% of the population over 15 years of age are married, 94% speak English and 1% speak Spanish. 76% of Plymouth residents were born in Michigan, 17% were born out of state, 1% were born outside of the United States and 6% were foreign born.