State Trunk Highway 29 (often called Highway 29, STH 29 or WIS 29) is a state highway running east–west across central Wisconsin. It is a major east–west corridor connecting the Twin Cities and the Chippewa Valley with Wausau and Green Bay. A multi-year project to upgrade the corridor to a four-lane freeway/expressway from Elk Mound to Green Bay was completed in 2005. The expansion served to improve safety on the route, which was over capacity as a two-lane road. The remainder of WIS 29 is two-lane surface road or urban multi-lane road.

WIS 29 passes through Pierce, St Croix and Dunn Counties in this section. The highway begins at its western terminus at U.S. Route 10, on the north side of Prescott. From this point, Highway 29 follows WIS 35 northeast to River Falls, passing the University of Wisconsin–River Falls campus. At the junction with WIS 65, WIS 35 turns northbound with WIS 65 while WIS 29 continues east. WIS 29 joins briefly with US 63 west of Spring Valley and turns eastbound upon its split one mile (1.6 km) south to head into Spring Valley. Upon leaving Spring Valley and Pierce county, the route heads northward into St Croix County and turns east towards Menomonie. WIS 29 does not pass through any municipalities while in this county, but it does cross WIS 128.

Upon entering Dunn County, the route passes through rural terrain and enters Menomonie's west side as Hudson Rd. The route turns northward onto Main street and passes west and north of the University of Wisconsin–Stout campus. WIS 29 turns east onto Stout Road along with US 12 and leaves the city to the east. The two routes proceed east for about 9 miles (14 km) and junction with Interstate 94. This interchange is the westernmost point of the multi-lane WIS 29 corridor. It is also the westernmost point of WIS 29 as a backbone route in Corridors 2020.

Between Elk Mound and Wausau, WIS 29 passes through Dunn, Chippewa, Clark and Marathon counties. West of CTH T, the route is an expressway. The route passes into the Chippewa Valley metropolitan area and south of Chippewa Falls as a Freeway and crosses U.S. Route 53 at a cloverleaf interchange in Lake Hallie. WIS 29 junctions with the southern terminus of WIS 178 southeast of Chippewa Falls then passes to the south of Lake Wissota State Park before crossing under Wisconsin Highway 27 in Cadott. WIS 29 passes south of Boyd and Stanley before exiting the county to the east.

In Clark County, WIS 29 meets WIS 73 in Thorp. the two routes exit the village to the east concurrently and WIS 73 splits to the south in Withee about 10 miles (16 km) east. WIS 29 continues east and passes south of Owen and Curtiss. At Abbotsford, WIS 29 and WIS 13 meet at a partial cloverleaf interchange between Abbotsford and Colby on the Clark and Marathon county line. Twelve miles east of Abbotsford, WIS 29 and WIS 97 meet at a diamond interchange. This is a key route for travelers between Wausau and Marshfield. East of this junction, WIS 29 follows a straight route that passes Edgar and meets WIS 107 at a diamond interchange on the north side of Marathon City, approximately 8 miles west of Wausau. WIS 29 enters Wausau as a freeway, junctions with the western terminus of WIS 52 approx. 1/2 mile west of US 51 at an eastbound off/westbound on style half-interchange. WIS 29 then immediately enters the new US 51 interchange, and turns south onto and follows US 51 for five miles (8 km), bypassing the downtown area to the south.

This stretch of the highway passes through Marathon, Shawano, Outagamie and Brown Counties. South of Wausau, WIS 29 turns off US 51 to the east at the northern terminus of I-39 and continues as freeway, passing through the villages of Rothschild and Weston. The freeway section ends at Ringle. As an expressway, the highway passes just south of Hatley and turns southeast for about four miles (6 km) before turning east again at the northern terminus of WIS 49.

The highway enters Shawano County about one mile (1.6 km) east of this junction. WIS 29 passes north and around Wittenberg. US 45 joins with the highway north of Wittenberg and the two routes run concurrently to where US 45 splits to the south at about two miles (3 km) east of the village. WIS 29 bypasses Tilleda and Thornton on the way towards Shawano At Shawano, the expressway becomes a freeway at the junction with CTH MMM (WIS 29 Business) and turns southeast to bypass Shawano to the south, diamond interchanges link the highway with WIS 22 and WIS 47 North / WIS 55 North as it pass south of the city. WIS 47 South and WIS 55 South follow WIS 29 east. WIS 47 splits to the south at the diamond interchange junction with WIS 117 south of Bonduel. WIS 29 (along with WIS 55) then returns to an expressway at the junction with CTH BE (WIS 29's former route). WIS 55 splits to the south at the diamond interchange junction with WIS 160 at Angelica and WIS 29 heads southeast to its junction with WIS 156 at the Brown County line.

About one mile (1.6 km) into Brown County, WIS 29 collects WIS 32 eastbound at the diamond interchange with CTH Y. WIS 29 very briefly(approx 1/2 mile!) passes through the northeast corner of Outagamie County and enters the village of Howard. The multilane expressway and the Backbone Corridor route end at US 41. WIS 32 turns south onto US 41 as WIS 29 continues into Green Bay as Shawano Avenue.

This section of the highway passes through Brown and Kewaunee Counties. In downtown Green Bay, WIS 29 turns north onto South Monroe Avenue for 4 blocks, joining with WIS 54 and turns east onto Main Street, splitting from WIS 54 and joining US 141 to leave the city to the southeast. The highways passes over I-43 without an interchange. WIS 29 splits to the east from US 141 at about 1-mile (1.6 km) north of US 141's southern terminus at I-43 in Bellevue. This provides the only access from I-43 to WIS 29. The highway passes through Poland and Henrysville as it exits Brown County to the east. In Kewaunee County, WIS 29 passes due east through Pilsen and north of Krok as a two lane road. The highway ends in downtown Kewaunee at WIS 42 on the shores of Lake Michigan.

Prior to 1926, Highway 29 was numbered Highway 116 from Minnesota to Chippewa Falls, Highway 16 from Chippewa Falls to Bellevue, and Highway 146 from Bellevue to Kewaunee. Highway 16 continued southeast from Bellevue along what became U.S. Highway 141 in 1926 to Manitowoc. What had been Highway 29 before 1926 became U.S. Highway 16 across the state.

Highway 29 has long been known as "Bloody 29" because of the prevalence of grisly fatal traffic crashes along significant portions of the highway. In 1988, a study was commissioned to examine upgrading the highway to a 4-lane divided highway. The changes would be made along 203 miles (327 km) of road from I-94, 2 miles (3.2 km) west of Elk Mound, to US 41 in Howard (suburban Green Bay). The final segment of the highway, connecting the east side of Chippewa Falls with the segment running north of Eau Claire, was opened to traffic on August 16, 2005. Of the total length, about 65 miles (105 km) of the highway meets Interstate standards. Most of the expansion was able to be completed with only minor additions to the already-existing easements, and as a result, the expanded roadway almost exactly matches the highway's original course. While traffic crashes have declined significantly, numerous memorials to those who lost their lives on the road still dot the route.

Highway 29 is the only Wisconsin state highway in WisDOT's Corridors 2020 Backbone Routes system.

The portion of WIS 29 between Chippewa Falls and Abbotsford roughly follows what used to be the Yellowstone Trail.

In 2007, the improvements to Highway 29 won a Wonders of Wisconsin Engineering Award from the American Council of Engineering Companies, Wisconsin Chapter. Four firms (Ayres Associates, Strand Associates, CH2M Hlll and Earth Tech) were honored for their work on the project in the chapter's 50th anniversary award program.

The US 51/WIS 29 expansion project is now completed in the Wausau area. This project has expanded the portions of Highway 29 that are co-signed with US 51 from 4 lanes to 6 lanes and reconstructed interchanges along the route to allow for higher bridge clearances, and higher capacity on/off ramps. The southern interchange where Highway 29 turns east off from US 51 was completed in late 2006. The northern interchange where WIS 29 turns west off of US 51 is now fully open to traffic. On September 17, 2010, the final ramp connecting WIS 29 Eastbound to US 51 northbound opened to traffic. Other upgrades to WIS 29 in the Wausau area include the segment from Wausau to Marathon City, where most at grade access will be removed, along with the construction of a new diamond interchange at CTH O. The paved center median will be replaced with a concrete barrier median, and the speed limit raised to 65 mph upon completeion of the project.

Over the past few years, corridor preservation studies have been underway to plan for the eventual conversion of WIS 29 to full freeway standards. Areas are being studied in Marathon, Shawano, and Brown Counties. Specifically between Abbotsford and Wausau in western Marathon County, as well as from Ringle in east central Marathon County through Shawano County to CTH J in the Village of Howard in Brown County near Green Bay.

Beginning in 2011, WIS 29 will be upgraded in Brown County, beginning at CTH J in the Village Of Howard, proceeding east to US 41. The WIS 29/US 41 Interchange will be upgraded to a "free-flow" freeway-to-freeway style interchange to allow for uninterrupted travel between the two highways. The upgrades will also include an interchange at CTH EB/Packerland Dr./Cardinal Ln and a grade separated overpass at CTH J. This project is expected to last until 2015. Work will also begin in the next few years on upgrading WIS 29 to freeway status from Packerland Drive westerly to the Brown/Shawano County Line.

In Dunn County, studies are now being conducted on the reconstruction of the WIS 29/I-94 interchange. The objective is to provide a free flow interchange between the two freeways, similar to the 51/29 interchange in Wausau, and the 41/29 interchange in Green Bay. This will be the final link in the WIS 29 project, having direct freeway to freeway interchanges at the three major junctions along the route.

(US 51)

(US 51)

(US 51)

Shown here as a terminus to the 4-lane expressway. WIS 29 is surface street here with a diamond interchange with the US 41 Freeway.

WisDOT is studying options for Highway 29 conversions to Interstate standards in three sections.

The section between I-94 and County Highway X's eastern exit is already designated as a freeway by WisDOT - despite the existence of several at-grade intersections between U.S. Highway 53 and I-94. WisDOT is studying options for upgrade of these intersections as part of the study. In addition, upgrades to the I-94 interchange with Highway 29 are also being considered. WisDOT is also studying options for upgrades to the highway to a freeway further east to Bruce Mound Ave. in Clark County.

The second section - between Wittenberg (U.S. Highway 45) and Green Bay (U.S. Highway 41) is also undergoing a study for planned upgrades of the highway to freeway standards. As it stands now, the Shawano bypass is the only section that is a freeway. The study is geared toward upgrading the rest of the section to Interstate standards.

The third section - between Ringle (County Highway Q) and Wittenberg (U.S. Highway 45) is at the preliminary stages for freeway upgrades. WisDOT is currently focusing on preserving right of way access for future upgrades.

Through various public input meetings held in the Wausau area, improvements to the segment of WIS 29 from WIS 107 at Marathon City easterly to 72nd Ave at Wausau are scheduled to begin in 2012. Improvements over the course of the project will include the construction of frontage roads, as well as the placement of a concrete barrier median down the currently paved median of WIS 29. Other improvements include construction of a diamond interchange just east of 120th Ave, with County Road O relocated on new alignment to this interchange. At the time of construction, all local road and private access to WIS 29 will be removed between WIS 107 and 72nd Ave. Future improvements to this stretch include an overpass at 152nd Ave.

As of December 2011, the DOT has proposed plans for eventual freeway conversion on their website for the segment of WIS 29 from WIS 13 easterly to WIS 107.

WIS 29 has four business routes: