Why, it's such a messy and nonsense unit system.

...this definition was retained for data derived from NAD27, but renamed the US survey foot to distinguish it from the international foot.[3] For most applications, the difference between the two definitions is insignificant – one international foot is exactly 0.999998 of a US survey foot, for a difference of about 1/8 inch (3 mm) per mile – but it affects the definition of the State Plane Coordinate Systems (SPCSs), which can stretch over hundreds of miles.[11]

What the fuck...

I'm convinced the only reason America keeps using such shitty imperial conversions is because it makes money for the cartographic lobby or something.