Chinook was born in Blackwater River Herd alongside her half-sister, Atna, having shared the same sire. Kitimat, Chinook's mother, had been stolen away by the lead stallion and had become pregnant with Chinook in her first year in the herd. Chinook grew up to be a sturdy young mare, and gave birth to her first foal, a colt named Chilako, after having been charmed by a bachelor who was later chased away by her father. Chilako was born the same year as Atna, but was killed by a cougar when he was two months old.

Shortly before Nechako and Atna left the herd, she would be stolen away by the same stallion who had charmed her the year before, but they would be separated in the onset of winter by a pack of wolves as they came into the Teekon Wilds. Alone, now, she has found the trail of other horses and follows them in hopes of joining a herd.