The Long Trail — Deborah Hopkinson

Klondike or bust!
Stowing away on the steamer Al-Ki was only the beginning of Davey's daring quest to find his uncle in the Klondike. Now he's camping in the rough-and-tumble town of Skagway, working for his photographer friend Erik Larsen, and preparing for his next challenge -- the steep, treacherous, hundreds-of-miles-long Chilkoot Trail.
When Erik falls ill on the trail, Davey fears he will not be able to go on -- until he gets help from a surprising ally.