Some ideas:
And hint of riches new and old.
I think this may refer to the gold rush that took place in Pike's Peak, and I'm sure there's gold pieces lingering. Also, pieces of gold were mostly found in nuggets: you'd never find a hole bar just lingering around. This part could be a complete gibberish referring to what's in the treasure themselves
Begin it where warm waters halt
I don't know yet. It could be reffering to somewhere outside Yellowstone though, where the geisers are. It may or may not refer to Colorado Springs as well.
And take it in the canyon down,
Not far, but too far to walk.
Put in below the home of Brown.
Okaay, regarding the home of Brown, I'm almost positive this is not to be taken literally. I can't exactly deduce why, but for some reason, I have an intuition it has to do with something with California and setlers crossing the Rocky Mountains to get to California.I just can't put my finger on it though. On the other hand, this can't be literal — Brown is an extremely common surname, amd there are at least about 6 different places that has Brown in their name.
From there it’s no place for the meek,
The end is drawing ever nigh;
There’ll be no paddle up your creek,
Just heavy loads and water high.
Regarding the no paddles andd heavy loads, I'm not too sure. I think it may hint that this is a waterfall (water high). One thing though, I think this hints that that you must go up the stream, so the elevation of treasu is somewhere up top. There may be a specific creek its referring to, but I doubt it, as ther is almost no creek that you wouldn't be allowed to paddle up... I'm probably wrong though. Its either that or the creek is frozen (see the line reffering to worth the cold).
If you’ve been wise and found the blaze,
Trailblazer perhaps. So it could refer to a pre-made road.
Look quickly down, your quest to cease
But tarry scant with marvel gaze,
Just take the chest and go in peace.
So why is it that I must go
And leave my trove for all to seek?
The answers I already know
I’ve done it tired, and now I’m weak
So hear me all and listen good,
Your effort will be worth the cold.
The Rockies do get pretty cold in the winter. Perhaps you have to travel during winter only?
If you are brave and in the wood
I give you title to the gold.
Side note:
I feel that this place must be somewhere legally accesible, but somewhere more obsure, like say the woods, to not draw attention. Also, i think there should be a noticible indicator in some sense, though not sure yet.
I found this link https://www.earthmagazine.org/article/trail-treasure-rocky-mountains that should be helpful