Decommissioned Highways in the United States
The landscape of American transportation is constantly shifting. As traffic patterns evolve and engineering standards advance, many roads that once served as primary arteries are stripped of their status. This process, known as decommissioning, occurs when a highway is removed from a numbered system, downgraded to a lower classification, or entirely demolished.
From the early days of the United States Numbered Highway System, short-lived routes were common. For instance, the early US 110 in Wisconsin had a brief tenure. By 1982, the fourteen shortest U.S. Numbered Highways ever created had all lost their "US" status.
The Mechanics of Highway Redesignation
Highway designations often change due to extensions or the creation of new route networks. When a highway is extended, it frequently absorbs and eliminates existing designations. A prime example is US 6; originally ending at the Hudson River in New York, it was extended to Long Beach, California. This expansion absorbed several existing routes, including Indiana State Road 6, portions of US 32 between Chicago and Omaha, the entirety of US 38 between Omaha and Denver, and California State Route 7 in the Mojave Desert. Later, during the 1964 Great Renumbering of California, US 6 was shortened to end at Bishop, California.
Another common driver of decommissioning is the rise of the Interstate Highway System—a network of high-speed, controlled-access freeways. As these faster routes are built, older highways are often supplanted. The most famous example is US 66, which connected Los Angeles and Chicago from 1926 until 1985 before losing its designation to the Interstates.
Partial and Total Decommissioning
Not all decommissioning is absolute. Some routes are only partially removed. In Michigan, segments of M-21 were replaced by Interstate 196 (from Holland to Grand Rapids) and Interstate 69 (between Flint and the Canadian border), while M-21 remained active between Grand Rapids and Flint. Similarly, in Lancaster, Ohio, US 33 was redesignated as US 33 Business after the main route was relocated to meet Interstate standards.
In other cases, highways are completely removed. Texas State Highway 9 was entirely decommissioned in favor of newer Interstates. Interestingly, the process can occasionally reverse; I-170 in Baltimore was removed in favor of US 40 after its parent route, I-70, was cancelled due to public opposition.
State-Level Changes and Abandonment
States frequently manage their own route designations based on infrastructure quality and economic utility. Some state routes are upgraded to Interstate standards, such as Pennsylvania Route 60 being largely replaced by I-376. Conversely, others are downgraded, such as US 61 in Minnesota becoming Minnesota State Highway 61 from Duluth to the Canadian border.
Economic shifts can also lead to abandonment. Arizona transferred Arizona State Route 62 to the Mohave County government after the closure of a mine in Chloride removed the road's primary economic purpose. In extreme cases, roads are physically destroyed. California State Route 480 was demolished after the 1989 Loma Prieta earthquake because the cost of retrofitting it for continued service was too high.
Policy and Urban Planning
The American Association of State Highway and Transportation Officials (AASHTO) has a policy that deprecates "Alternate", "Bypass", and suffixed routes, especially those that are short and confined to a single state. Examples include US 6A in Connecticut, the former US 30S in Ohio, and the US 71 bypass around Kansas City, which was replaced by Interstate 435 and Missouri Route 291.
Urban planning also plays a role. In Indianapolis, Indiana removed all state and US Highway designations within the Interstate 465 beltway. This resulted in the truncation of US Highway 136, the total deletion of Indiana State Road 100, or the diversion of routes onto the beltway. A similar process occurred in Fort Wayne following the 1998 completion of Interstate 469.
Alternative Uses and Historical Preservation
Decommissioned roads do not always disappear; some are repurposed for non-automobile use. The Abandoned Pennsylvania Turnpike, which became overcapacity after World War II, has been converted into a bike and pedestrian trail. Because it follows the alignment of the failed South Pennsylvania Railroad, it is also considered an unofficial rail trail.
Despite the shift toward superhighways, some routes maintain cultural significance. US 66 remains a point of interest for antiquarians and commercial ventures. Although unofficial, "Historic Route US 66" markers designate much of the old road, some of which is celebrated for its literary connection to John Steinbeck's The Grapes of Wrath.
Key Facts
- US 66 is the most iconic example of a highway decommissioned in favor of the Interstate system.
- AASHTO policy discourages the use of suffixed, alternate, or bypass routes.
- Economic collapse, such as the mine closure in Chloride, Arizona, can lead to state routes being transferred to local government.
- Natural disasters, like the 1989 Loma Prieta earthquake, can lead to the total demolition of highways (e.g., CA State Route 480).
- Repurposing allows old highways to become recreational assets, such as the Abandoned Pennsylvania Turnpike trail.
| Route | Original Status | New Status / Outcome | Primary Reason |
|---|---|---|---|
| US 66 | U.S. Highway | Decommissioned | Suppplanted by Interstates |
| PA Route 60 | State Route | I-376 | Upgraded to Interstate standards |
| AZ State Route 62 | State Route | County Road | Economic purpose ended (mine closure) |
| CA State Route 480 | Interstate System | Demolished | Earthquake damage/Retrofitting costs |
| PA Turnpike (section) | Turnpike | Bike/Pedestrian Trail | Overcapacity/Bypassed |
Frequently Asked Questions
Why are some U.S. highways decommissioned?
Highways are typically decommissioned when they are replaced by faster, more direct Interstate Highways, when they no longer serve an economic purpose, or when they are absorbed into larger route extensions.
What happens to a road after it is decommissioned?
The outcome varies: it may be downgraded to a state or county road, redesignated as a "Business" route, converted into a recreational trail, or in some cases, completely demolished.
What is the role of AASHTO in highway naming?
AASHTO (American Association of State Highway and Transportation Officials) sets policies for the numbering system, including the current deprecation of suffixed, alternate, and bypass routes.
Can a decommissioned highway be brought back?
While rare, designations can shift back. For example, I-170 in Baltimore was removed in favor of US 40 after the planned I-70 parent route was cancelled.
Are there any famous decommissioned roads still visited today?
Yes, US 66 is a prime example. Although it is no longer an official U.S. Highway, it is marked by unofficial "Historic Route US 66" signs and attracts tourists due to its cultural and literary significance.