Sharpest curve on the C&TS - 20 degrees
Sharpest Curve on the DRGW west of Chama - 24 degrees (Monero Canon).
Sharpest Curve on the Silverton Branch - 24 degrees At several spots: Hermosa Hill, "Granite Point", Highline, and a couple of others.
Marshall Pass and the Monarch Branch both had lots of 24 degree curves.
Somebody told me once upon a time that the Durango Loop is 27 degrees, but since then there has been added a second track to the inside of it
RGS had lots of 24 degree curves and a few 30 degree ones on branches.