Delmar is a town in Sussex County, Delaware, United States, on the Maryland border along the Transpeninsular Line. Its motto is "The Little Town Too Big for One State." The population was 1,597 at the 2010 census, an increase of 13.5% over the previous decade. It is part of the Salisbury, Maryland-Delaware Metropolitan Statistical Area and a suburb of Salisbury, MD. When added with "twin city" Delmar, Maryland, the total population of the town was 4,600 at the 2010 Census.