Hudson to Lake Delton US 12 crosses the
St. Croix River from Minnesota concurrent with I-94 into
St. Croix County.
Wisconsin Highway 35 (WIS 35) joins both routes upon their entry into Wisconsin and exits south east. US 12 leaves I-94 further east from the eastern WIS 35 exit, treks north, and parallels the Interstate. The highway crosses
WIS 65 in
Roberts and passes through
Hammond over a segment to
Baldwin, where it crosses
US 63. US 12 passes through
Woodville east of Baldwin and crosses
WIS 128 in
Wilson, west of the
Dunn County line. Roughly into Dunn County, US 12 passes through
Knapp then turns southeastward, connecting with
WIS 79 further; it then joins
WIS 25 (North Broadway Street) to the south in Menomonie. US 12 turns east onto
WIS 29 (Main Street East) in downtown Menomonie, and the two routes follow Stout Road east out of the city. The highways meet an interchange with I-94, then split one half of a mile () east in
Elk Mound at the junction with
WIS 40. US 12 passes through Elk Mound and enters
Eau Claire County. US 12 merges with
WIS 312 east (North Crossing) for before turning south onto Clairemont Avenue, bypassing downtown Eau Claire to the south and west.
WIS 37 joins with US 12 on the southwest side of the city. Access to
WIS 93 is provided via
US 53. The interchange between US 12 and US 53 in
Altoona is Wisconsin's first
single-point urban interchange. US 12 continues east out of the
Eau Claire–Chippewa Falls metropolitan area and passes through
Fall Creek, where it turns southeastward to join
WIS 27 south in
Augusta. The two highways briefly join
US 10 on the
Jackson County line in
Fairchild. US 12 and WIS 27 turn southward and pass through
Humbird in
Clark County and into
Jackson County. US 12 and WIS 27 cross
WIS 95 in
Merrillan and
WIS 54 in Black River Falls. US 12 and WIS 27 also split in Black River Falls. US 12 follows I-94 to the southeast past
Millston and into
Monroe County. The highway crosses I-94 (with no access) south of
Kirby and junctions with
WIS 21 on the north side of Tomah at an interchange with the Interstate. US 12 passes through Tomah and joins with
WIS 16 on the south side at the junction with
WIS 131 near
Mill Bluff State Park. The highways continue paralleling
I-90 and I-94 southeast and pass through
Oakdale and into
Juneau County. WIS 16 turns east onto
WIS 13 north as
WIS 23 west turns south onto US 12. These highways follow the
Wisconsin Dells Parkway south into the heart of the Wisconsin Dells tourism district, passing such attractions as
Noah's Ark Water Park, the Wisconsin Ducks boat tours,
Kalahari Resort,
Mt. Olympus Water & Theme Park,
Wilderness Territory, and
Tommy Bartlett Show. WIS 23 turns west onto Monroe Avenue as US 12 turns southeast and crosses the Interstates.
Lake Delton to Cambridge At the I-90/94 interchange, US 12 becomes a freeway that bypasses Baraboo that goes just south of the Grasser Road overpass. The highway becomes an expressway just north of Lehman Road and remains so until a few miles north of Sauk City.
WIS 60 briefly joins US 12 in Sauk City and
WIS 78 crosses the
Wisconsin River concurrently with US 12 into
Dane County. US 12 merges with
US 14 at University Avenue. The freeway continues south and passes the interchanges of Greenway Blvd, Old Sauk Road, and Mineral Point Road (CTH-S). The freeway then turns eastward and passes the interchanges of Gammon Road, Whitney Way, and Verona Road/Midvale Blvd, where
US 151 and
US 18 join the freeway, creating a concurrency of four US Highways for a few miles. During the four-way concurrency, the freeway passes the interchange of Seminole Highway (only accessible from the westbound side), the
University of Wisconsin–Madison Arboretum, and the interchanges of Todd Drive, Fish Hatchery Road (CTH-D), and Park Street, where
US 14 leaves to go south and
US 151 north into downtown Madison. US 12 and US 18 continue east into
Monona and cross the Upper Mud Lake channel. The highways meet
US 51 at Stoughton Road, then interchange with
I-39 and
I-90 on the southeast side of Madison. US 12 and US 18 continue as an expressway east of the Interstates, junctioning with
WIS 73 in
Deerfield and splitting, with US 12 turning southeast into
Jefferson County in
Cambridge. WIS 89 turns off US 12 at its junction with
WIS 59. WIS 59 East follows US 12 briefly before turning north into the city. US 12 passes through
La Grange and turns south at the junction with
WIS 20 to follow
WIS 67 south. US 12 turns southeast off WIS 67 onto a freeway northeast of Elkhorn. The highway crosses over
WIS 11 with no access (although access is provided via nearby I-43), then interchanges with
I-43. Access for Lake Geneva is provided at
WIS 120 and
WIS 50 as US 12 passes the city to the east. The highway turns south into
Genoa City, where the freeway ends and US 12 follows the crossroad into
Illinois. ==History==