"The narrative begins with Nick Adams, Hemingway's protagonist and alter-ego, having just gotten off the train in Seney, a town in Michigan's Upper Peninsula. He hikes into the wilderness and fishes for trout. The problem is that the Two-Hearted River lies about 20 miles north of Seney and flows into Lake Superior. On foot, it's virtually impossible to get there with Nick's apparent speed. The Fox River -- a perfectly good stream for brook trout -- runs right through the town, on its way to Lake Michigan.
Hemingway visited Seney with a couple of friends in 1919. Wouldn't he have just fished the Fox?"
This was settled long ago, in the 1960's in fact by a real fishing writer, one of the greats, and one of the U.P.'s own sons. Read the chapter about this topic in Robert Traver's ( née John Voelker) book "Trout Magic". Some other good stuff in there as well.
