Agriculture is Saskatchewan's main industry and taking grain to elevators was first accomplished by horse and cart, to be replaced around World War I by trucks. Long haul trucking flourished between 1950 and 1970, and aided by the completion of the Trans-Canada Highway over the 1960s. Since the 1970s, there are 17 times the number of grain trucks. and 95 per cent of goods transported now are hauled by truck across the Saskatchewan.
Provincial Highway 4, the first road across the province, followed the surveyed grade of the transcontinental CPR between the Alberta and Manitoba border. Prior to the 1940s, this route would have simply following on the township road allowances, all at right angles across the province.
Interestingly, the surveys varied between Manitoba and Saskatchewan. In Manitoba there were 100 foot (30m) road allowances every 1 mile (1.6km), while in Saskatchewan the road allowance was 66ft (20m) every two miles (32 km), which required a two mile correction at the border to smooth out the highway survey line.
The highway across Saskatchewan connecting #1 in Alberta and the #1 in Manitoba was completed across relatively flat land and rolling prairie agricultural plains, along a relatively straight route.
The highway generally runs west to east along the route, following parallel with the transcontinental Canadian Pacific Railway route that was built across the province in 1885. This route pass through major urban centres in the province (from west to east): Swift Current, Moose Jaw and Regina. Premier Tommy Douglas opened Saskatchewan's stretch of the Trans-Canada in August 1957.
1957 saw the Saskatchewan portion of the Trans-Canada Highway come to completion, the first province to finish their section in Canada.
In recent decades the entire length across Saskatchewan was "twinned" by having two lanes in each direction, at a cost of $217 million. In 2008, the final stretch of the highway was twinned between Moosomin and Wapella to complete the twinned corridor.
Here are some history notes, organized by Itinerary Segment (from west to east):