Once the fiber is finished, Kentucky leaders say, it will connect the commonwealth to the world. That’s the thinking behind KentuckyWired, an ambitious public–private partnership to bring high-speed internet capacity to every corner of the state. The project showcases the promise and the risk in public–private partnerships. Some critics are calling it wishful thinking.

Highways were hard to build in Appalachia. Information highways are no less difficult to realize today. Abundant limestone and do…