Delmar is a town in Sussex County, Delaware state. It is located on the Maryland border along the Transpeninsular Line. Its population was 1,597 at the 2010 census, an increase of 13.5% over the previous decade. It is part of the Seaford, Delaware Micropolitan Statistical Area and a suburb of Salisbury, Maryland.
The name of Delmar was derived for the railroad center from the states whose line it straddles - DELaware and MARyland.