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.
The Town of Delmar was founded in October 1859 with the extension of the Delaware Railroad to the southern boundary of Delaware. The Transpeninsular Line was responsible for the founding of this unique bi-state town because the Charter of the Delaware Railroad Company permitted only the building of a railroad within the State of Delaware and the charter of the corresponding railroad company in Maryland permitted only the laying of railroad track within the State of Maryland. Thus, in 1859, the two respective railroads met and the town of Delmar was born. The name is a portmanteau of the states whose border this railroad center straddles - Delaware and Maryland.
The Town of Delmar grew slowly until 1884 when the New York, Philadelphia and Norfolk Railroad (in 1921 acquired by the Pennsylvania Railroad) completed a railroad from Pocomoke City, Maryland to Cape Charles, Virginia and also established a ferry service across the Chesapeake Bay between Cape Charles and Norfolk, Virginia. These new developments immediately made the Delmarva Peninsula an important link between the north and south. The Town of Delmar, being the midway town of the Delmarva Peninsula and already a railroad terminal, was the point for trains to change crews and locomotives and also a center for maintenance of the rolling equipment.