The Madison runs straight through Ennis and is the reason most visitors come. It is wide, fast, gravel-bottomed and full of wild rainbow and brown trout, and the stretch from Quake Lake down to Ennis Lake is arguably the most reliable dry-fly water in the Lower 48. You can wade fish from a dozen public access points within fifteen minutes of town, or hire a guide to take you down it in a drift boat for about US$650 a day. The famous "salmonfly hatch" in late June and early July draws fishermen from around the world; the hopper fishing in August and September is, if anything, even better.
Even if you do not fish, the river is worth walking along. The cottonwoods give shade, the views back to the Madison Range are spectacular, and the wildlife — eagles, otters, the occasional moose — is genuinely abundant. Several outfitters in town rent waders, rods and boats by the day.