U.S. Route 12 in Indiana

Section of U. S. Highway in Indiana

U. S. Route 12 (US 12) is a part of the United States Numbered Highway System that runs from Aberdeen, Washington, to Detroit, Michigan. In the U. S. state of Indiana, it is part of the state road system. US 12 enters the state concurrent with US 20 and US 41 in Whiting. The 46.258 mile (74 km) of US 12 that lie within Indiana serve as a major conduit. Some of the highway is listed on the National Highway System (NHS). Various sections are rural two lane highway, urbanized four lane undivided highway, and one way streets. The easternmost community along the highway is Michiana Shores at the Michigan state line. US 12 passes through urban areas and wood lands, parallel to the Lake Michigan shoreline. The highway is included in the Lake Michigan Circle Tour and passes through Indiana Dunes National Park. Historical landmarks along the highway include the Miller Town Hall, Beverly Shores station, and the Old Michigan City Light. A memorial highway designations have been applied to the route since 1917, named for the Civil War Union Army unit. US 12 was first designated as a U. S. Highway in 1926, concurrent with US 20 west of Michigan City. A section of the highway originally served as part of the Dunes Highway, a connection between Gary and Michigan. US 12 replaced the original State Road 43 (SR 43) designation of the highway which dated back to the formation of the Indiana state road system. SR 43 ran from the Illinois state line through Gary to Michigan City and ended at the Michigan state line. In the early 1920s, it was the most important route between Chicago and Detroit and in 1922 the first sections started being paved. The Indiana State Highway Commission, later renamed Indiana Department of Transportation (INDOT), removed US 20 from the section east of Gary in the early 1930s. Most of the route has since been supplanted by Interstate 94 (I 94) and the Indiana Toll Road.

Only one segment of US 12 is included in the NHS. That is the segment that is concurrent with US 20 from the Illinois state line to the split with US 20 in East Chicago. The NHS is a network of highways that are identified as being most important for the economy, mobility, and defense of the nation. The highway is maintained by INDOT like all other U. S. Highways in the state. The department tracks the traffic volumes along all state highways as a part of its maintenance responsibilities using a metric called annual average daily traffic (AADT). This measurement is a calculation of the traffic level along a segment of roadway for any average day of the year. In 2010, INDOT figured that the lowest traffic levels were 3,120 vehicles and 350 commercial vehicles used the highway daily near Ogden Dunes. The peak traffic volumes were 30,510 vehicles and 2,430 commercial vehicles AADT along the section of US 12 at the Illinois state line, concurrent with US 20 and US 41. The highway has been designated as the Iron Brigade Memorial Highway to honor the Civil War Union Army unit; it has the same designation in Michigan, Wisconsin, and Illinois.

US 12 enters Indiana concurrent with US 20 and US 41, at which point it passes under the Indiana Toll Road. The road passes both commercial and industrial areas between Wolf Lake and Horseshoe Hammond. US 12, US 20, and US 41 are concurrent until US 41 turns south on Calumet Avenue. Both US 12 and US 20 head southeast toward East Chicago, where US 12 turns east while US 20 continues south. The route heads east through East Chicago as a four lane undivided highway passing through mostly residential areas. The road heads south concurrent with SR 912, passing through mainly industrial area between East Chicago and Gary. The two routes have an interchange at SR 312 and access to the Indiana Toll Road, via an interchange at Gary Avenue. The road has two bridges with the first passes over the Grand Calumet River and the other passing over the Indiana Toll Road and the South Shore Line. After passing the rail line, the road has an interchange with US 20, this interchange is the southern end of the SR 912 concurrency. US 12 follows US 20 east toward Downtown Gary, as a four lane divided highway. The two highways pass through residential areas and crosses the Lake Shore and Michigan Southern Railway owned by Norfolk Southern Railway, before Downtown Gary. At Bridge Street in Gary, the road becomes one way streets, with westbound on Fourth Avenue and eastbound on Fifth Avenue. In Downtown Gary it has an intersection with SR 53, locally known as Broadway. The streets also pass by the historical Knights of Columbus Building and the old Ralph Waldo Emerson School building. East of Downtown Gary, the road passes by U. S. Steel Yard, the home of the Gary SouthShore RailCats, an independent professional baseball team. The one way streets end and the road becomes a six lane divided highway, known as Dunes Highway. The Dunes Highway passes between the South Shore commuter rail line and residential houses. East of Gary the route has a signalized intersection with the northern terminus of I 65.

After I 65, the road has a trumpet interchange with I 90. In the far eastern portion of Gary, US 12 and US 20 split for the final time, although US 20 closely parallels US 12 for the next 20 mile (32 km), sometimes coming within 0.2 mile (0 km). US 20 follows a slightly more southerly route to Michigan City (via Portage and Porter), while US 12 passes through Indiana Dunes National Park and retains the name "Dunes Highway". After splitting from US 20, US 12 becomes a mostly rural two lane highway, passing through the woodland.

The Old Chicago Road was an important road from 1900 to 1910; it was later renamed the Dunes Highway. The Dunes Highway Association engineers envisioned the Dunes Highway a "state of the art" 40 feet (12 m) concrete highway with a 100 feet (30 m) right of way. In August 1919, commission director H. L. Wright tentatively designated the Dunes Highway as SR 43, to be 20 feet (6 m) wide. Narrower than anticipated, the new concrete highway was still superior to most Indiana roads, which in the mid 1920s were gravel or dirt with paved sections only between the larger towns. Dunes Highway construction began in 1922 under the guidance of Gary contractor Ingwald Moe and construction engineer Ezra Sensibar. The designation was changed to US 12 and US 20 in 1926 when the U. S. Numbered Highway System was created. The two routes were concurrent from Illinois to Michigan City, with the rest in Indiana as only being US 12. In 1930, US 20 was moved to a new alignment south of US 12. This left US 12 on its current alignment without US 20. The route did not change between 1931 and 2002, with only work being maintenance. Then in 2003, the state of Indiana rerouted US 12 onto SR 912 from Columbus Drive to US 20. The route was changed to make room for the Gary/Chicago International Airport runway expansion project.