Delaware Route 9 is a 58-mile state highway that connects with Delaware Route 1 at the Dover Air Force Base (only just less than a mile south of the southern terminus of the Korean War Veterans Memorial Highway) to Interstate 95 in the City of Wilmington. Much like their U.S. Highway counterparts (Delaware State Routes, with some exceptions, follow the AASHTO system used for numbering U.S. highways), Delaware Route 9 runs east of Delaware Route 1, but unlike the more heavily-traveled DE 1, DE 9 is a designated scenic highway, and has a commercial truck restriction between Dover A.F.B. and Delaware City. Delaware's Coastal Heritage Greenway follows much of Delaware Route 9 south of Wilmington, linking many important sites along the Delaware Bay.
Past Bombay Hook, the road intersects DE 6 and then crosses over the Smyrna River on a high-level crossing (this was a drawbridge in the past) and then splits off south of Odessa with DE 299. The road, after crossing over several more tidal rivers, then draws up to the headwaters of the Delaware Bay, at Augustine Beach, in which the Salem Nuclear Power Plant in New Jersey can be easily seen. DE 9 then enters the small town of Port Penn, and continues north to Delaware City.
Past Port Penn, DE 9 continues north through the Delaware marshlands on a more modern two lane road with emergency shoulders. For four miles, the road crisscrosses with several swamps and drainage canals until the road crosses the Chesapeake and Delaware Canal on the Reedy Point Bridge. Opened in 1966, the high-level crossing replaced a vertical-lift drawbridge as part of the 1960s canal improvement project that eliminated all locks on the canal as well as the building of both the Summit Bridge (U.S. Route 301 and Delaware Routes 71 and 896) and the Canal Lift Bridge for the Pennsylvania Railroad.
North of the canal itself, the road then crosses over both Fort Dupont and the Governor Bacon Health Center before entering Delaware City itself. Just past the canal, but before Delaware City, DE 9 crosses over the Delaware City Channel, which was before the 1920s, the eastern terminus of the C & D Canal. The Delaware City Channel, which connects the present-day canal with the Delaware River, serves as a marina, but access to the canal is restricted due to the drawbridge, which DE 9 uses, is currently out of service. After going through Delaware City, the road then continues north to the intersection with DE 72 at the Valero (formerly Texaco) Delaware City Oil Refinery, at that point the scenic road and commercial truck restrictions end.