Interesting question, especially since I do virtually no trout fishing anymore because I prefer to fish for steelhead.
There are two streams in Montana that are special trout fishing havens, and neither is very well known so I will not name them herein; but anyone with some knowlege of Montana would have no real trouble finding them. One is a public spring creek that is located a dozen miles or so from Three Forks, MT. The other is the very top three miles of a well known river on the west slope of the Continental Divide, that was among Gary LaFontaine's favorite.
And in Pennsylvania there is a terrific river flowing through a canyon for nearly its whole length that has in recent years been re-habilitated in its lower reaches that holds many fond memories, including a 10lb brown caught about 1:00 a.m. one August night. This river helps form the western boundary of the Pocono Mountains in its middle section.