Yarmouth is a town in Cumberland County, Maine, United States, located twelve miles north of the state's largest city, Portland. The town was settled in 1636 and incorporated in 1849. Its population was 8,349 in the 2010 census. As of 2015's estimation, this is about 0.6% of Maine's total population.Yarmouth is part of the Portland–South Portland-Biddeford Metropolitan Statistical Area.The town's proximity to the Atlantic Ocean and its location on the banks of the Royal River, which empties into Casco Bay less than a mile away, means it is a prime location as a harbor. Ships were built in the harbor mainly between 1818 and the 1870s, at which point demand declined dramatically. Meanwhile, the Royal River's four waterfalls within Yarmouth, whose Main Street sits about 80 feet above sea level, resulted in the foundation of almost sixty mills between 1674 and 1931.The annual Yarmouth Clam Festival attracts around 120,000 people over the course of the three-day weekend.