Wisconsin Highways: Since 1997.

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"STH"..."CTH"..."Highway"? Help!

You may have noticed this website uses certain abbreviations and nomenclature that are a bit out of the norm, at least for everyday conversation. This page describes why such terms are used and defines just what they mean. Use the information here to make your visit at the Wisconsin Highways website more enjoyable and, by all means, feel free to contact the webmaster if you have any remaining questions!

Route Definitions


County Trunk Highway, where xx is any combination of one to three letters. Sometimes written elsewhere as "County Trunk xx", "County Highway xx", "Highway xx" or "County xx". Also, the designation itself is never placed in quotes, as seems to be popular in some places and media, as there is no actual need or use for the quotation marks.


Federal Forest Highway, where nn is the route designation. These are routes within National Forests and are often referred to as simply "Forest Highway nn."


Interstate Highway, where nn is the Interstate route designation, such as I-39, I-41, I-43, I-90, I-94, I-535, I-794 or I-894.


Michigan state trunkline highway designation, where nn is a number between 1 and 553. For some unknown reason, the people of Michigan have never referred to their state highways as "State Route nn" or "Highway nn", etc. Rather, all state routes in Michigan are referred to as "M-nn".


State Route, where nn is a numeric designation. A generic term for "State Route" used in many states, such as in neighboring Illinois and Iowa.


Wisconsin State Trunk Highway, where nn is a number between 11 and 794. Generally referred to elsewhere and in usual speech as "Highway nn", however this can be confusing as US Highways and sometimes even Interstate Highways are also referred to as "Highway nn". "STH" is a term which has been used by WisDOT and its predecessors since the dawn of the state trunk highway system in the state, however the department generally uses the shorthand "WIS nn" in documents for public consumption.


Minnesota Trunk Highway, where nn is a designation from 1 to 988C. Oftentimes written elsewhere as "MN-nn"


US Highway, where nn is the US Highway designation, such as US-2, US-8, US-10, US-12, US-14, US-18, US-41, US-45, US-51, US-53, US-61, US-63, US-141 or US-151. For many decades, Wisconsin had a policy of never duplicating route number designations anywhere in the state, but this rule has been relaxed in recent times. So, while you still will not find a US-41 and STH-41 (or "Highway 41" and "Highway 41" in common usage) in the state, this site uses the more technical term for precision and to avoid confusion. (Business US Highways, which are generally locally-maintained in Wisconsin, are written "BUS US-nn".)



With the definitions out of the way, some may ponder the question of why the different uses and descriptors for highway route designations? This is an interesting question for those who follow linguistics or even for transportation enthusiasts. Interesting in that as one travels around North America, it quickly becomes clear that what highways are called in one state or region is not the same as in other areas. For this reason, among others, this website uses the actual route designation ("US-12" instead of "Highway 12") as a way to eliminate the confusion caused by these regional differences. A quick, and by no means comprehensive, run-down of the highway-descriptor terms used in the local vernacular in some places follows.

Wisconsin. At some point in the linguistic evolution in Wisconsin, every highway became known as simply that: "Highway." In the very early days there were only one type of highways, State Trunk Highways, so no different names needed to be assigned to different types. Soon after, the County Trunk Highway system came into being, although with lettered routes instead of numbered ones as on the state system, so the general term "Highway" could still be used with little confusion. "Highway 57" is a state route while "Highway P" would be a county route.

When the US Highway system debuted in 1926, it added another wrinkle, but since US Highways are simply state highways bearing a coordinated, nationally-based route designation and because Wisconsin implemented a rule that there would be no duplication of route designations between the US and State Trunk Highway systems, the "Highway nn" usage stuck, even when referring to US Highways. The introduction of the Interstates in 1956–57 initiated the first 'crack' in the "everything's-a-Highway" method of describing routes, with most people and the media referring to these routes as "Interstate 94," for example, or simply "I-94." However, references to "Highway 94," while less common, are still heard and seen.

Michigan. Neighboring Michigan is somewhat unique in North America in that the general reference to "Highway nn" or "Route nn" is almost never heard or used in print. For example, I-94 in Michigan is always "I-94," while US-41 is "US-41" and their state trunkline routes, such as M-28, are referred to using the "M" designator and never include the words "State Trunkline," "State Highway," "State Route" or even just "Highway," and would be "M-28." Why Michiganders have always been overly astute when it comes to highway designations is unclear, but it is a trait generally unknown to the rest of North America. (Coloradans and Kansans, though, often refer to their state highways as C-nn and K-nn, respectively.)

Illinois. While most definitely not alone, Illinoisians refer to their "Highways" as "Routes." Although many other states and regions also do this, it is interesting to note that when a highway crosses 42°30' N latitude (the Wisconsin-Illinois state line), it transforms from "Highway nn" to "Route nn". For example, US-41 in Wisconsin is commonly referred to as "Highway 41," while US-41 in Illinois becomes "Route 41." "Route nn" is also used in neighboring Indiana and further east in Ohio.

California. The usage"Route nn" or "State Route nn" is also utilized in California to describe their highways, however the "Highway nn" method is sometimes used. California's Interstates, as in "Interstate 5," seem to be rarely be referred to as "Routes," as in "Route 5," though. One very unique thing, however, concentrated more in Southern California, is the use of "the" as the route descriptor for freeways, leaving off "Route," "Highway," "I-," or "US-". For example, I-405 is referred to as "the 405" while US-101 is similarly called "the 101." This tends to only be used for freeways.

Canada. Canada seems to be a bit less varied in their colloquial terms for their highways, generally settling on "Highway nn," much the same as Wisconsin has, when referring to their highways.


Have any other interesting observations regarding what people call their highways? Drop the webmaster a line if you do!