Cumberland is a city in and the county seat of Allegany County, Maryland, United States. At the 2020 census, the city had a population of 19,07…Cumberland is a city in and the county seat of Allegany County, Maryland, United States. At the 2020 census, the city had a population of 19,075. Located on the Potomac River, Cumberland is a regional business and commercial center for Western Maryland and the Potomac Highlands of West Virginia. It is the primary city of the Cumberland metropolitan area, which had 95,044 residents in 2020.