It is good to see Harry Majors back with his encyclopedic knowledge and analysis of the history of mountaineering in Washington. What Harry did in meticulously analyzing Henry Custer's cryptic 1859 journals of the Northwest Boundary Survey in his "Northwest Discovery" series in the 1980's, is beyond belief, and the post here on Mox is very enlightening.
As far as the origin of the name "Twin Spires," a piece of this historic name puzzle was found on the top of one of the minor summits along the Ridge of Gendarmes when I climbed it on 7/4/85 (while Russ Kroeker stayed in camp, Shoe-Gooing his delaminated boot sole back on).
Inside of a white, red, and blue Johnson & Johnson Waterproof Band-Aid (Borated Pad) metal box was a piece of crumpled paper that read,
Sept 20, 1939 S.W. peak
of south peak, Twin Needles
(own name)
We aren't very ashamed
to turn back on this baby.
It's got everything
Will Thompson
Calder Bressler
Ptarmigan Club, Seattle
We'll be back!
So it looks like Thompson and Bressler (not Bill Cox, as CAG, p.128 reads) came up with the "Twin" idea. Since there were already "Twin Needles" in the Southern Pickets, named by Strandberg, Degenhardt, and Martin in 1932, perhaps Beckey made the alteration to "Spires."