Highway 21 begins at Highway 1 approximately east of Strathmore in Wheatland County and travels north, passing near the village of Rockyford and it reaches a four-way stop at Highway 9 between Beiseker and Drumheller, where it crosses into Kneehill County. It continues north past the village Carbon to the intersection of Highway 27 east / Highway 582 west, beginning concurrency with Highway 27. Highway 21 continues to the town of Three Hills, home of Prairie Bible Institute, passing along the town's eastern edge. North of Three Hills, the CN rail line begins to run parallel to the highway, serving most of the communities along the route. Highway 27 departs from Highway 21 towards Olds, about south of the town Trochu. Highway 21 passes the hamlet of Huxley and the access road toDry Island Buffalo Jump Provincial Park before entering Red Deer County; the Kneehill / Red Deer county boundary also signifies the transition from the prairie to aspen parkland ecosystem, with increasing foliage. Highway 21 bypasses Elnora and Lousana prior to Delburne, skirting its western edge on a bypass constructed in the 1980s. North of Delburne, Highway 21 reaches a T intersection with Highway 595 and turns east for along Township Road 380, then north at Range Road 231, the former alignment through Delburne. The roadway narrows for the following as it heads towards the Red Deer River, which it crosses at the Content Bridge. North of the Red Deer River, it briefly enters Stettler County, crossing Highway 11 and Highway 12. Highway 21 turns west and follows Highway 12 for entering Lacombe County, before turning north, about east of the village of Alix. It passes by the hamlet of Mirror before entering Camrose County, passing northwest of Buffalo Lake. The route bypasses Bashaw, concurrent with Highway 53, then continues north past Ferintosh and the hamlets of New Norway and Duhamel, crossing the Battle River at an area locally known as Ross' Flats. Highway 21 intersects Highway 13 at the locality of Ervick, about west of the city ofCamrose, home of the Augustana Faculty of the University of Alberta and Big Valley Jamboree; Highway 21 is considered the main north-south highway serving Camrose despite not entering city limits. It continues north past the hamlet of Armena and village of Hay Lakes, entering Leduc County just south of the hamlet of New Sarepta, into the eastern portion of the Edmonton Metropolitan Region. North of the hamlet Looma, it enters Strathcona County and reaches an interchange with Highway 14. It becomes a divided highway, passing along the eastern edge of Sherwood Park prior to an interchange at Highway 16. Highway 21 continues north to the city of Fort Saskatchewan in which it ends at Highway 15.
History
The southern terminus of Highway 21 was originally at Highway 9 in the village of Beiseker, travelled north for along present-day Highway 806 to the village of Acme, travelled east for approximately along present-day Highway 575, before turning north towards Three Hills. In, Highway 21 was realigned to travel due south from Three Hills to Highway 9, and was later extended to Highway 1 near Strathmore, while the former section was renumbered to Highway 21A until, when it was renumbered to Highway 26, and again renumbered in to its present designations. The section from Fort Saskatchewan to Highway 16 was originally designated as Highway 55. By 1960, Highway 21 terminated at Highway 14 southwest of Edmonton. In the 1970s, Highway 21 was extended north from Highway 14 past Sherwood Park to Highway 16, while Highway 55 was renumbered and became part of Highway 21. The section of Highway 21 previously designated as 55 was twinned in the 1980s, and the section adjacent to Sherwood Park was completed in late 2009.
Future
Alberta Transportation has long term plans to replace the Content Bridge across the Red Deer River with a new crossing north of Delburne. Right-of-way is protected from the Highway 595 intersection to Highway 11 southwest of Alix, as well as from the current Highway 21 north / Highway 12 intersection south to Highway 11 – internally designated as Highway 921. There is no timeline on construction. Alberta Transportation, in partnership with the City of Edmonton, City of Fort Saskatchewan, Strathcona County, and Sturgeon County, is also studying a new North Saskatchewan River crossing in northeast Edmonton that would include a new roadway from the Highway 15 / Highway 28A intersection to Highway 21 south of Fort Saskatchewan. The study is still in the early stages, but proposals show that Highway 21 might be realigned so that through traffic would flow from Highway 16 to the new bridge and tie into Highway 28A. The final alignment has not been determined and it is not yet known if it would be designated as part of Highway 21. The proposed bridge and its connecting roads will not be constructed for another 25 to 35 years. There are also long-term plans to upgrade Highway 21 to expressway/freeway standards from the northeast river crossing to Highway 625 as part of a High Load/Heavy Haul bypass connecting Nisku to northeastern Alberta and Fort McMurray.
