An island in the air : a story of singular adventures in the Mesa country
by Ingersoll, Ernest, 1852-1946; McCullough, W. A. (William A.), ill; Lawrence, T. Cromwell, ill; Macmillan Company. pbl; Norwood Press. prt
Im not good enough at american geography yyo be sure that the story takes place here
https://en.m.wikipedia.org/wiki/Mesa_County,_Colorado
But i can tell you that this is a book for readers the age of ca 13, following a band of travellers over the rocky mountains. Adventures abound, and the book also contains some science and history worked into the story
