Complex sentence: Early settlers floated down the Columbia River from The Dalles to reach Western Oregon; in 1845, Sam Barlow built a road around the south side of Mount Hood, which served as the final leg of the Oregon Trail.
Split into simpler sentences: Early settlers floated down the Columbia River from The Dalles to reach Western Oregon. In 1845, Sam Barlow built a road around the south side of Mount Hood, which served as the final leg of the Oregon Trail.