The highway, which first came into existence in the late 1970s, was originally a two-lane road signed as Delaware Route 14, but was truncated to Milford when the Delaware Department of Transportation adopted a U.S. Highway-style system for its state routes. From the early 1970s to 1995, the highway ended at is what is now U.S. Route 113, but in the mid-1970s, the DOT studied a "Dover Extension" of the Delaware Turnpike, which evolved into today's Korean War Veterans Memorial Highway.
Past the inlet, Delaware Route 1 continues north through the state park, passing lookout towers used by the U.S. Army's Coastal Artillery forces during World War II, until the road enters Dewey Beach, a popular "fun spot" in the same cailber as that of Fort Lauderdale, Florida. It is here in Dewey Beach that Delaware Route 1A branches off and heads towards Rehoboth Beach, while Route 1 curves towards the left and then crosses over the Lewes and Rehoboth Canal on a high-level, twin span crossing (completed in the mid-1980s) before reabsorbing Route 1A. Between the northern junction of Route 1A and Lewes, Route 1, now a six-lane road, passes through an array of outlet shopping centers in Midway (known collectively as the "Rehoboth Outlets"), before intersecting with U.S. Route 9 and Delaware Route 404 near Lewes. U.S. Route 9 allows a direct access to the Cape May-Lewes Ferry to the Garden State Parkway and the New Jersey shore, while Delaware Route 404 allows access to the Chesapeake Bay Bridge, via U.S. Route 50 near Denton, Maryland.
North of Delaware Route 14, the Milford Bypass portion of Delaware Route 1 ends with the junction of Route 1 with U.S. Route 113. Prior to 2004, both Delaware Route 1 and U.S. Route 113 continued north together to Dover Air Force Base as a multiple highway route, but after numerous petitions by DelDOT, AASHTO, which governs the regulation of designating Interstate and U.S. Highways, allowed DelDOT to truncate U.S. Route 113 at this interchange. Ironically, prior to 1992, the Del. Route 1/U.S. Route 113 interchange served as the northern terminus for Del. Route 1, but with the construction of the Korean War Veterans Memorial Highway, DelDOT extended the Del. Route 1 designation north of this interchange to prevent a "gap" between the Fenwick Island-Milford section and the toll highway.
Past U.S. Route 113, the highway continues north towards Dover, passing Frederica (on a high-speed bypass), where it intersects Delaware Route 12, and Little Heaven before crossing over the St. Jones River on a high-level crossing that was built in the mid-1980s as part of a U.S. Route 113 widening project between Dover and Milford. Past the St. Jones River crossing, Del. Route 1 intersects with Delaware Route 9, a two-lane rural road that, prior to the completion of the Korean War Veterans Memorial Highway, served as a "bypass" around the usually congested U.S. Route 13.
After passing through the toll plaza in Dover, which has, since 2004, both cash and high-speed E-ZPass lanes, Del. Route 1 intersects with U.S. Route 13 for the first time, north of both the toll plaza and Dover International Speedway. Between Dover and Wilmington, Del. Route 1 will intersect with U.S. Route 13 a total of four times, with indirect access to the highway a total of five times, all of them via Delaware State Highway routes or with U.S. Route 40.
North of the first Del. Rt. 1/U.S. Rt. 13 interchange, the highway roughly parallels U.S. Route 13 through the northern fringes of Dover, interchanges with U.S. Route 13 in the southern part of Smyrna, and enters New Castle County to the east of Smyrna. At the third interchange with U.S. Rt. 13, which served as a temporary northern terminus between 1992 and 2003, the highway crosses over U.S. Rt. 13 and then travels for the next eight miles (13 km) past the small rural community of Townsend, before crossing over the Appoquinimink River and intersecting with Delaware Route 299 to Odessa and Middletown. Past Del. Route 299, Del. Route 1 then crosses over U.S. Route 13 and the Drawyer Creek and then intersects with Delaware Route 896 in Boyds Corner.
After Del. Route 896, the road then crosses over U.S. Route 13 before reaching the Biddle Corner Toll Plaza, the first toll plaza on the East Coast to have both high-speed E-ZPass and cash lanes, and, with some design changes, has served as a model for dual-speed mainline toll barriers on both the Pennsylvania Turnpike, New Jersey Turnpike, as well as the Garden State Parkway and Atlantic City Expressway. Passing through the toll barrier, the highway then crosses the Chesapeake and Delaware Canal on the massive steel and concrete Chesapeake and Delaware Canal Bridge, which was originally opened in 1995 as a replacement for the aging St. Georges Bridge, but now serves as an integral part of the Delaware Route 1/U.S. Route 13 corridor between Dover and Wilmington. It is also north of the toll plaza that Del. Route 1 becomes a six-lane highway, with the six lanes going approximately five miles (8 km) until Del. Route 1 splits off with U.S. Route 13 (which "rides along" with Del. Route 1 north of Delaware Route 72) in Tybouts Corner.
North of the Del. Route 1/U.S. Route 13 split, the road, now back to four lanes, starts a short five mile (8 km) trip north towards I-95/Delaware Turnpike, passing U.S. Route 40 and Delaware Route 273 before merging on with Delaware Route 7 near the Christiana Mall in Christiana. After merging with Del. Route 7, the Del. Route 1/7 combination continues north until it intersects with I-95/Delaware Turnpike at a classic cloverleaf interchange, and then immediately interchanges with Delaware Route 58 near Churchmans Crossing. After the Route 58 interchange, the Route 1 designation is dropped, and the now at-grade highway becomes just Route 7.
Even on the toll road between Dover and Wilmington, there are plans to widen the highway between Tybouts Corner and I-95/Delaware Turnpike to six lanes, as a need to reduce congestion, as well as rebuilding the Del. Rt. 1/I-95 cloverleaf interchange to one with high-speed ramps, allowing southbound and northbound traffic to access I-95 without having to "mix" in with merging traffic (the new Del. Rt. 58 bridge over I-95/Del. Turnpike, completed in 2006, being long enough to accompany the additional lanes). In addition to the expansion projects, plans are underway to build an "extension" of the highway, which will carry the U.S. Route 301 designation, that will bypass Middletown and allow an alternative route to Baltimore, Maryland and Washington, D.C., via the Chesapeake Bay Bridge, without having to travel on the heavily congested I-95/John F. Kennedy Memorial Highway on Maryland's Western Shore.
Other plans, including rebuilding Del. Route 1 to a "semi-freeway" (similar in nature to U.S. Route 301 in Maryland) have also been floated, but the future currently lies in the the possible privatization of both Del. Route 1 and the Delaware Turnpike, as well as the possible upgrading of the highway to an Interstate Highway route (most likely Interstate 101). If an Interstate 101 is built, it will most likely connect with Delaware Route 1 at Dover A.F.B. (via the short-distanced "Puncheon Run Connector," a low-speed grade-separated highway connecting Del. Route 1 with U.S. Route 13 near Camden), and with current reductions in federal spending, and may serve as "Maryland-Dover Section" of the Korean War Veterans Memorial Highway, bringing the highway almost up to the same state-to-state classification as that of both the Pennsylvania Turnpike and the New Jersey Turnpike.
| County | Location | Mile | # | Destinations | Notes |
|---|---|---|---|---|---|
| Sussex | Fenwick Island | ||||
| Bethany Beach | 6.08 | ||||
| Dewey Beach | 17.17 | ||||
| Rehoboth Beach | Interchange | ||||
| Oyster House Road | Interchange; no southbound entrance | ||||
| 18.93 | |||||
| Midway | 21.13 | ||||
| Carpenters Corner | 22.55 | – Cape May-Lewes Ferry | South end of US 9 overlap | ||
| Five Points | 23.67 | US 9 west / US 9 Bus. east / DE 404 to DE 23 / DE 1D – Georgetown | North end of US 9 overlap | ||
| Milton | 30.46 | ||||
| 32.68 | |||||
| Milford | |||||
| 39.91 | Interchange; northbound exit and southbound entrance | ||||
| 41.42 | Interchange | ||||
| Kent | |||||
| Northeast 10th Street – North Milford | |||||
| 43.96 | Interchange; southbound exit and northbound entrance | ||||
| Thompsonville Road – Thompsonville, South Bowers | |||||
| Frederica | 49.89 | ||||
| Bowers Beach Road – Bowers Beach | |||||
| Clapham Road – Magnolia, Rising Sun, Moores Lake | Former US 113 Alt. north | ||||
| Road 107 – Magnolia | Interchange | ||||
| Dover AFB | 56.22 | ||||
| South end of freeway | |||||
| 57.2 | 92 | Dover AFB Commercial Gate | Northbound exit and entrance | ||
| 57.8 | 93 | Dover AFB Main Gate, Visitors | |||
| 59.0 | 95 | Former US 113 north | |||
| 60.2 | 97 | – Salisbury, Norfolk | No northbound exit | ||
| Dover | 60.8 | 98 | Southbound exit and northbound entrance | ||
| Dover Toll Plaza | |||||
| 64.6 | 104 | ||||
| Smyrna | 70.8 | 114 | |||
| New Castle | 75.8 | 119 | Signed as exits 119A (south) and 119B (north) southbound | ||
| Odessa | 84.5 | 136 | |||
| Boyds Corner | 88.2 | 142 | |||
| Biddles Corner | Biddles Corner Toll Plaza | ||||
| St. Georges | 92.0 | 148 | Southbound exit and northbound entrance | ||
| Chesapeake and Delaware Canal Bridge | |||||
| Tybouts Corner | 94.5 | 152 | South end of US 13 overlap | ||
| 96.9 | 156 | , New Jersey, New York | North end of US 13 overlap; signed as exits 156A (SR 71) and 156B (US 13) southbound | ||
| Bear | 99.4 | 160 | – Elkton, State Road | ||
| Christiana | 100.7 | 162 | |||
| 101.9 | 164 | South end of DE 7 overlap; signed as exits 164A (Mall Road) and 164B (DE 7) southbound | |||
| 102.5 | 165B | , Philadelphia | |||
| 102.8 | 165A | , Baltimore | |||
| Churchmans Crossing | 103.1 | 166 | |||
| 103.1 | Continuation beyond DE 58 | ||||