[a-priori]

Another example is Saskatchewan, Canada. Like Colorado, its borders, on all four sides, are defined by latitudes and longitudes.

[niftich]

Saskatchewan actually has an unusual border on its east with Manitoba, in which a series of north-running meridians are interrupted by west-running jogs. This newspaper piece [1] reflects on the story behind this boundary.

[1] http://www.theglobeandmail.com/opinion/why-the-zigzag-betwee...

[jessriedel]

But the curvature of the Earth means Colorado is closer to a rectangle :)