A ridge about 75 to 80 feet (23 to 24 m) in elevation extends along the western boundary of the state and separates the watersheds that feed Delaware River and Bay to the east and the Chesapeake Bay to the west.
Since almost all of Delaware is a part of the Atlantic coastal plain, the effects of the ocean moderate its climate.
In the northern third of the state are found Northeastern coastal forests and mixed oak forests typical of the northeastern United States.
Trap Pond State Park, along with areas in other parts of Sussex County, for example, support the northernmost stands of bald cypress trees in North America.
The state was named after the Delaware River, which in turn derived its name from Thomas West, 3rd Baron De La Warr (1577–1618) who was the ruling governor of the Colony of Virginia at the time Europeans first explored the river.
It was initially colonized by Dutch traders at Zwaanendael, near the present town of Lewes, in 1631.
Most of the boundary between Delaware and Pennsylvania was originally defined by an arc extending 12 miles (19.3 km) from the cupola of the courthouse in the city of New Castle.
This border extends all the way east to the low-tide mark on the New Jersey shore, then continues south along the shoreline until it again reaches the 12-mile (19 km) arc in the south; then the boundary continues in a more conventional way in the middle of the main channel (thalweg) of the Delaware River.
Delaware provides government subsidy support for the clean-up of property "lightly contaminated" by hazardous waste, the proceeds for which come from a tax on wholesale petroleum sales.
Before Delaware was settled by European colonists, the area was home to the Eastern Algonquian tribes known as the Unami Lenape, or Delaware, who lived mostly along the coast, and the Nanticoke who occupied much of the southern Delmarva Peninsula.Delaware was one of the 13 colonies participating in the American Revolution.