What is the only Canadian province whose borders form a rectangle?

Saskatchewan is a prairie and boreal province in western Canada, the only province without natural borders. It has an area of 651,900 square kilometers (251,700 sq mi), nearly 10 percent of which (59,366 square kilometers (22,900 sq mi)) is fresh water, composed mostly of rivers, reservoirs, and the province's 100,000 lakes.

Saskatchewan is a landlocked province with large distances to moderating bodies of waters. As a result, its climate is extremely continental, rendering severe winters throughout the province. Southern areas have very warm or hot summers. Midale and Yellow Grass near the U.S. border are tied for the highest ever recorded temperatures in Canada with 45 °C (113 °F) observed at both locations on July 5, 1937. In winter, temperatures below −45 °C (−49 °F) are possible even in the south during extreme cold snaps.

As Saskatchewan's borders largely follow the geographic coordinates of longitude and latitude, the province is roughly a quadrilateral, or a shape with four sides. However, the 49th parallel boundary and the 60th northern border appear curved on globes and many maps. Additionally, the eastern boundary of the province is partially crooked rather than following a line of longitude, as correction lines were devised by surveyors prior to the homestead program (1880–1928).