British Columbia Highway 3 is a two-lane undivided highway that becomes Alberta Highway 3 at the border in mountainous terrain, paralleling a branch of the Canadian Pacific Railway.
 It first crosses over to the south side of the railway and passes through the centre of Island Lake on a causeway, part of which is natural terrain.
 It curves through communities of the Municipality of Crowsnest Pass on the south side of Crowsnest Lake, crossing the Crowsnest River and reaching Highway 40 at Coleman.
 It continues alongside the railway through Blairmore, again crossing the Crowsnest River and bisecting the community of Frank and the rubble of the Frank Slide, a major landslide that killed more than 70 people in 1903.
The highway, the Crowsnest River, and the railway meander east into the Municipal District of Pincher Creek No.
 9 and Burmis from which Highway 507 splits south to Beaver Mines and forms an alternate route from the west into Pincher Creek.
 Highway 3 curves northeast to the hamlet of Lundbreck which it bypasses, and from which Highway 22 begins and runs north.
 The first of four former alignments of Highway 3 (all of which are now designated as Highway 3A) passes through Lundbreck, splitting from Highway 3 prior to the hamlet and rejoining it 3 km (1.9 mi) later.

East of Lundbreck and Cowley, the highway crosses Castle River to Highways 6 and 785 north of Pincher Creek.
 It briefly parallels the creek for which the town was named before crossing it and reaching Brocket, and Highway 786 which meets Highway 507 southeast of Pincher Creek.
 Highway 3 follows the Oldman River to Fort Macleod, approximately 30 km (19 mi) east of Brocket.
Just prior to Fort Macleod, the highway enters the Municipal District of Willow Creek No.
 26 and Highway 810 splits south to the communities of Ardenville and Glenwood after which Highway 3 widens to a divided highway.
 It meets Highway 2 at a trumpet interchange, and diverges into a one-way road pair through Fort Macleod at a reduced speed limit of 50 km/h (31 mph), concurrent with Highway 2.
Highway 811 turns north from Highway 3 in central Fort Macleod to cross the Oldman River on a historic alignment of Highway 2.
 At the Fort Macleod Health Centre, Highways 2 and 3 curve southeast to leave the town as the one-way roads rejoin into a divided highway.
 The concurrency ends as Highway 2 splits south as a two-lane highway to Cardston and the United States border at Carway.
Highway 3 bends back to the northeast, now designated as the Red Coat Trail and carrying CANAMEX traffic destined for the primary border crossing on Highway 4 at Coutts.

The divided highway continues northeast from Fort Macleod with a speed limit of 110 km/h (68 mph), paralleling the Oldman River.
 It curves east to bypass Monarch to the south and crosses the river, entering Lethbridge County.
 Highway 3 formerly passed through Monarch until the 1990s construction of the bypass; that route is now designated as Highway 3A and meets Highway 23 east of the town which then joins Highway 3 north of the confluence of the Oldman and Belly Rivers.
 After curving southeast, Highway 509 splits southwest to Stand Off.
 Highway 3 intersects 51 Avenue, the main access for the town of Coalhurst.
 Westview Drive splits into West Lethbridge at a partial interchange and for less than one kilometre it forms the third route designated as Highway 3A.  Highway 3 continues east, entering the city of Lethbridge as a freeway and meeting Highway 25/University Drive at a partial cloverleaf interchange.
 Highway 25 runs north to Picture Butte, while University Drive connects to the University of Lethbridge and is the main thoroughfare of West Lethbridge.
British Columbia Highway 3 is a two-lane undivided highway that becomes Alberta Highway 3 at the border in mountainous terrain, paralleling a branch of the Canadian Pacific Railway.  It first crosses over to the south side of the railway and passes through the centre of Island Lake on a causeway, part of which is natural terrain.  It curves through communities of the Municipality of Crowsnest Pass on the south side of Crowsnest Lake, crossing the Crowsnest River and reaching Highway 40 at Coleman.  It continues alongside the railway through Blairmore, again crossing the Crowsnest River and bisecting the community of Frank and the rubble of the Frank Slide, a major landslide that killed more than 70 people in 1903. The highway, the Crowsnest River, and the railway meander east into the Municipal District of Pincher Creek No. 9 and Burmis from which Highway 507 splits south to Beaver Mines and forms an alternate route from the west into Pincher Creek.  Highway 3 curves northeast to the hamlet of Lundbreck which it bypasses, and from which Highway 22 begins and runs north.  The first of four former alignments of Highway 3 (all of which are now designated as Highway 3A) passes through Lundbreck, splitting from Highway 3 prior to the hamlet and rejoining it 3 km (1.9 mi) later.
East of Lundbreck and Cowley, the highway crosses Castle River to Highways 6 and 785 north of Pincher Creek.  It briefly parallels the creek for which the town was named before crossing it and reaching Brocket, and Highway 786 which meets Highway 507 southeast of Pincher Creek.  Highway 3 follows the Oldman River to Fort Macleod, approximately 30 km (19 mi) east of Brocket. Just prior to Fort Macleod, the highway enters the Municipal District of Willow Creek No. 26 and Highway 810 splits south to the communities of Ardenville and Glenwood after which Highway 3 widens to a divided highway.  It meets Highway 2 at a trumpet interchange, and diverges into a one-way road pair through Fort Macleod at a reduced speed limit of 50 km/h (31 mph), concurrent with Highway 2. Highway 811 turns north from Highway 3 in central Fort Macleod to cross the Oldman River on a historic alignment of Highway 2.  At the Fort Macleod Health Centre, Highways 2 and 3 curve southeast to leave the town as the one-way roads rejoin into a divided highway.  The concurrency ends as Highway 2 splits south as a two-lane highway to Cardston and the United States border at Carway. Highway 3 bends back to the northeast, now designated as the Red Coat Trail and carrying CANAMEX traffic destined for the primary border crossing on Highway 4 at Coutts.
The divided highway continues northeast from Fort Macleod with a speed limit of 110 km/h (68 mph), paralleling the Oldman River.  It curves east to bypass Monarch to the south and crosses the river, entering Lethbridge County.  Highway 3 formerly passed through Monarch until the 1990s construction of the bypass; that route is now designated as Highway 3A and meets Highway 23 east of the town which then joins Highway 3 north of the confluence of the Oldman and Belly Rivers.  After curving southeast, Highway 509 splits southwest to Stand Off.  Highway 3 intersects 51 Avenue, the main access for the town of Coalhurst.  Westview Drive splits into West Lethbridge at a partial interchange and for less than one kilometre it forms the third route designated as Highway 3A.  Highway 3 continues east, entering the city of Lethbridge as a freeway and meeting Highway 25/University Drive at a partial cloverleaf interchange.  Highway 25 runs north to Picture Butte, while University Drive connects to the University of Lethbridge and is the main thoroughfare of West Lethbridge.
Alberta Highway 3