Horse & Pony Books:
SALTO: A HORSE OF THE CANADIAN MOUNTIES
aka HORSE OF THE DEEP SNOWS
(DODD, MEAD & CO. [USA] 1950)
ILLUSTRATED BY HARRY A. BURNE
Reprinted by the original publishers in 1954 with a different title: HORSE OF THE DEEP SNOWS.
SUMMARY: Set in Canada. Salto is the mount of Constable Park Langdon of the Canadian Mounted Police. Together they fight crime in the wilderness area of Northern Canada.
TRAIL OF THE PINTO STALLION
(DODD, MEAD & CO. [USA] 1951)
SUMMARY: Adventure story based on true events. Nat Kane travels with the expedition of Captain Bonneville into the Rockies in order to try and find his missing friend Brent and his pinto stallion Kiowa.
TRAIL OF THE PINTO TO OREGON
(DODD, MEAD & CO. [USA] 1957)
Not sure if this book has any relation to the above, be it a sequel or indeed the same book re-titled. If you have any information regarding it please contact me.
In the USA the books are reasonably easy to find. Quite a bit rarer elsewhere.