WIS 21 begins at the intersection of
WIS 16,
WIS 71 and
WIS 27. The highway then follows WIS 16/WIS 71,
running concurrently east for about before turning north off the concurrency. WIS 21 proceeds northeast, following the
La Crosse River and passes through Fort McCoy. The highway then turns eastward and follows alongside the Tarr and Sparta creeks, passing through
Tunnel City. WIS 21 crosses
US Highway 12 (US 12) and
Interstate 94 (I-94) on the north side of
Tomah. The highway continues east from there to junction with
WIS 173 west of
Wyeville and then crosses into
Juneau County. WIS 21 passes through the
Necedah National Wildlife Refuge during its stretch of straight route to
Necedah. The highway crosses
WIS 80 within Necedah and crosses the
Wisconsin River at about east of the village. WIS 21 enters
Adams County at the river, just south of
Petenwell Lake. WIS 21 junctions with
WIS 13 north of
Friendship. The highway also provides indirect access to
Roche-a-Cri State Park via WIS 13. WIS 21 crosses
I-39 and
US 51 at
Coloma in
Waushara County. The highway passes through the village just east of the Interstate. After passing through
Richford at County Trunk Highway B (CTH-B), WIS 21 gradually curves northward to junction with CTH-Y—where it turns sharply eastward and junctions with
WIS 22 and
WIS 73 north in
Wautoma. WIS 21 follows WIS 73 south for before turning east again of the concurrency near Silver Lake.
WIS 152 junctions with the routes about northwest of the eastern concurrency terminus. The highway passes through
Lohrville and
Redgranite and junctions with
WIS 49 south of
Auroraville. WIS 21 enters
Winnebago County east of WIS 49. WIS 21 crosses
WIS 116 in
Omro. The highway then enters the greater Oshkosh area and junctions with
US 41 along Omro Road. WIS 21 continues along Omro Road, Oshkosh Avenue and Congress Avenue, ending at
US 45 (Algoma Boulevard) on the northwest side of Oshkosh after crossing the upper
Fox River east of
Lake Butte des Morts. File:Wisconsin Highway 21.jpg|WIS 21 turns through downtown Sparta File:WisconsinHighway21EastTerminus.jpg|Eastern terminus at US 45 File:Wisconsin State Highway 21 in Tomah.jpg|WIS 21 in Tomah with I-94 and US 12 junction in the background == History ==