According to his backstory, William Preston was an American from Chicago, who originally came to the Yukon to help solve his own father's murder. Working with the Mounties assigned to the case brought out his natural talents as a policeman, and Preston was invited to join the force after he helped track down and capture the killers. See more
Sergeant Preston of the Northwest Mounted Police with Yukon King, swiftest and strongest lead dog breaking the trail in the relentless pursuit of lawbreakers, in the wild days of the Yukon. Back to the days of the Gold Rush, as Sergeant Preston, with his wonder dog, Yukon King, meets the challenge of the Yukon.
[map of Yukon Territory appears on screen
This is the Yukon . . .