The Letort is where American fly fishing grew up, and it remains its sternest schoolroom. A limestone spring creek rising near Carlisle in the Cumberland Valley, it is small, slow, clear and watercress-choked — the water Vince Marinaro and Charlie Fox studied until they reinvented dry-fly fishing around its impossibly selective wild browns. The lime-rich springs keep it cold and fertile and even-tempered all year; the bed is silt, gravel and rooted cress, the surface a slow mirror that forgives nothing. The trout are few, large, wild and so wary that catching one is a genuine event spoken of afterward. This is terrestrial water — the cricket, the cress bug, the ant — fished fine and far off on the lightest tippet you can bear. Wading is mostly avoided on the soft bottom; you kneel in the grass, watch, and try not to be seen.

Wading: Soft silt bottom, total exposure