Complex sentence: He then traversed a portion of that valley, followed Sinclair Pass, recrossed the Kootenay and using White Man's Pass reached the Bow River valley, near the site of present-day Canmore, Alberta.
Split into simpler sentences: He then traversed a portion of that valley, followed Sinclair Pass, recrossed the Kootenay and using White Man's Pass reached the Bow River valley. He would have been near the site of present-day Canmore, Alberta.