DE 15 crosses the Providence Creek into New Castle County and the name becomes Clayton Greenspring Road as it passes through farm fields and woods with some homes. The route turns west onto Vandyke Greenspring Road and skirts the southern edge of the Blackbird State Forest, curving to the west-northwest and crossing Blackbird Creek. DE 15 turns north onto Dexter Corner Road before it continues west onto Blackbird Station Road, curving to the northwest. The route crosses the Maryland and Delaware Railroad's Northern Line at-grade before heading across Barlow Branch and turning north at the Ebenezer Church Road intersection to remain along Blackbird Station Road. Upon crossing Caldwell Corner Road, the road name changes to Dogtown Road and it curves to the northwest again. The route runs through agricultural areas, crossing the Appoquinimink River, and turns north-northeast onto Levels Road. DE 15 passes to the west of a residential neighborhood before turning northwest at a roundabout with St. Annes Church Road to remain on Levels Road and reach an intersection with DE 299.