Barnum is an unincorporated community and coal town in Mineral County, West Virginia, United States. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. Barnum lies on the North Branch Potomac River along a line of the Western Maryland Railroad no longer in operation. Barnum has excellent trout fishing along its banks and offers many o…Barnum is an unincorporated community and coal town in Mineral County, West Virginia, United States. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. Barnum lies on the North Branch Potomac River along a line of the Western Maryland Railroad no longer in operation. Barnum has excellent trout fishing along its banks and offers many opportunities for anglers.