Why the Iowa class sits near the battlecruiser boundary

Are the Iowa-class ships fast battleships or battlecruisers?

They are best treated as fast battleships, though their tradeoffs place them close to the battlecruiser edge of the spectrum.

The answer treats the distinction between fast battleships and battlecruisers as a spectrum rather than a rigid label. Iowa sacrificed some protection and range relative to more heavily protected contemporary American concepts in order to achieve speed. If those slower battleship designs had also been built, the contrast could make Iowa look much more like their battlecruiser counterpart. Because they were not, the Iowa class became the United States' operational fast battleship design. Classification therefore depends not only on a ship's specifications, but on the fleet and design alternatives against which it is compared.