A part of the Catskills, and the region farther S., drains into Delaware Bay through the Delaware river.
Tide-water Maryland is afforded rather unusual facilities of water transportation by the Chesapeake Bay, with its deep channel, numerous deep inlets and navigable tributaries, together with the Chesapeake and Delaware Canal, which crosses the state of Delaware and connects its waters with those of the Delaware river and bay.
Wit continued decrease of altitude south-eastward, the crystalline belt dips under the coastal plain, near a line marked by the Delaware river from Trenton to Philadelphia in Pennsylvania, and thence south-south-westward through Maryland and Virginia past the cities of Baltimore, Washington and Richmond.
The lower portion of the Delaware river has been entered by the sea as the result of the depression of the land, giving a harbour, at the head of which developed the city of Philadelphia.
Work was begun on the system in 1826 and was continued without interruption until 1840, when the completed or nearly completed portions embraced a railway from Philadelphia to Columbia on the Susquehanna, a canal up the Susquehanna and the Juniata from Columbia to Hollidaysburg, a portage railway from Hollidaysburg through Blair's Gap in the Alleghany Front to Johnstown on the Conemaugh river, a canal down the Conemaugh, Kiskiminetas, and Allegheny rivers to Pittsburg, a canal up the Susquehanna and its west branch from the mouth of the Juniata to Farrandsville, in Clinton county, a canal up the Susquehanna and its north branch from Northumberland nearly to the New York border, and a canal up the Delaware river from Bristol to the mouth of the Lehigh; considerable work had also been done on two canals to connect the Ohio river with Lake Erie.