Michigan Highways: Since 1997.

Michigan Highways website header graphic
M-22 & M-109 junction route signage in Glen Arbor, Michigan

Historical Overview

Michigan has long been known as a pioneer in many aspects of roads and highways. Many of today's commonplace road features were originally conceived of or perfected in Michigan. Some of these innovations and improvements had their genesis in the burgeoning automobile industry, which blossomed in Michigan in the late-19th and early-20th centuries. Because of all the new motorized vehicles on the road, certain improvements were borne of necessity. Later, Michigan remained at the forefront of highway-related improvements and today continues in that role.
1948 Packard Sedan and Just a few of Michigan's contributions to the motoring public include:

As noted in the list above, Michigan was the second state in the US—the second jurisdiction anywhere in the world, for that matter—to set up and mark a state trunkline system. The numbering and posting of state highways began in neighboring Wisconsin, where the state legislature grew increasingly frustrated with the haphazard system of "Auto Trails" then in use. These Auto Trails were generally set up by commercial interests (e.g. tire manufacturers) trying to increase use of their products or tourism entities trying to get motorists to pass through their towns. As these Auto Trails were far from being impartial, many meandered far and wide from the most direct or best course between points. Plus, a single roadway may have a dozen or more different Auto Trails designated along it, making for a very confusing situation! Wisconsin in 1917 and Michigan a year later decided to do away with the multitudes of confusing Auto Trails names and routes and simply number their state trunklines systematically.
Even before Michigan posted numbers on its state trunklines, the state legislature passed the "State Trunk Line Act" in 1913 authorizing the designation of a state highway network totalling almost 3,000 miles of roadway. The act stipulated the newly-created State Highway Department would design, build and maintain highway bridges 30 feet in length or longer, if the county or local government improved three miles of adjacent road. This was the beginning of what would later turn into an over 9,000-mile system of roads, highways and freeways cris-crossing the state and reaching from Copper Harbor to Luna Pier.
Over the years, highway routes were added, re-routed, re-numbered and removed from the system. Individually, these changes number in the thousands and range from a half-mile realignment of a two-lane highway to the complete removals of entire highway designations, like US-112 in 1961 and US-27 in 2002. This website attempts to chronicle as many of these changes as humanly possible. A comprehensive history of public roads in Michigan can be found in The History of Roads in Michigan. Most of the individual route changes are documented within the histories of each highway designation in the Highway Listings pages. You may also find interesting historical information within the In Depth portion of the website.