Oregon visitors can reach Mount Jefferson in the Mt. Jefferson Wilderness Area, Willamette National Forest. Be sure to hire a local guide for trips into the Willamette National Forest.
The peak of the second tallest mountain in the State of Oregon, Mount Jefferson, also known as Seekseekqua, was first seen by the Lewis and Clark Expidition from the mouth of the Willamette River.
At the end of what could only have been a miserable day, William Clark wrote in his journal: “We made 22 Miles only to day the wind and a strong current being against us all day, with rain. Discovered a high mountain S E. Covered with Snow which we call Mt. Jefferson.”
The day was March 30, 1806, and Clark, Meriwether Lewis, and the Corps of Discovery had been on the homeward trail for just five days since leaving Fort Clatsop. They named the towering peak after President Thomas Jefferson, the only volcanic peak they named of the five observed rising over the Cascade Range. At 10,495 feet in elevation, Mount Jefferson ranks as the second highest peak in Oregon.
Mount Jefferson is a stratovolcano that has erupted periodically over the past 300,000 years. The volcano can produce large, explosive eruptions, and the last one was about 15,000 years ago. Smaller events have also occurred, including lava flows and lahars. Much of Mount Jefferson’s history is unknown since erosion by glaciers has long since erased the evidence of past eruptions. Even today, the mountain is covered in glaciers, making it a significant challenge for climbers.