I was curious about this question so I did a google search. Curiously NASA came up several times as the most efficiently (or one of the most efficiently) run large department in the federal govt. I was surprised as it seems that historically they've had programs with massive cost overruns and delays similar to the Pentagon.
What do people say here and why?
TVA. Providing power, flood control, navigation supporting commercial river transportation, conservation and recreational benefits, with sound management, but putting money back in the federal coffers every year.
The TVA is awesome, but they are a federal
corporation.
IDK if you would call that a dept or not.
Created as a Federal program, now a self sustaining federal program, proving what can be done by government for the benefit of the citizens, not tied directly to creating corporate profits for selected private entities. I grew up 35 miles from Kentucky Dam. They built Barkley dam just a few miles away, providing more power, flood control and navigation on the Cumberland and creating the Land Between the Lake recreational area, where I have camped, hiked, explored numerous times on my own and with my family, as well as with the Boy Scouts of America. Always liked TVA.
TVA, More Power To Ya!