Here's the skinny on the name.
Ferdinand Hayden gave the name "Pilot Peak" referring to the leader ("pilot") of mining expeditions. Index was originally named "Dog Turd" (it look like it from the right angle) but they renamed it "Index Finger" (which it also looks like from the Cooke City angle). Come mapping time, the name "Index" was applied.
Hayden's 6th Report, 1873
The Yellowstone Story; Aubrey Haines
Select Peaks; Turiano
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