 The Okanogan Valley was the traditional homeland of the Syilx ( also called Okanogan ) Native Americans , whose territory extended north into what is now Canada . The Syilx acquired horses in the mid @-@ 18th century , which helped them expand northward . They first met non @-@ native traders and missionaries in the early 19th century . The Syilx participated in trade fairs held at Kettle Falls and at the mouth of the Fraser River . Trading networks strengthened after the acquisition of horses in the mid @-@ 18th century . 
