The observatory is currently closed (July 2020) but the trails are open for hiking. From $18.00. $14.40. Although people are able to climb Mount St. Helens year-round, late spring through early fall is the most popular season. Lots of views of the mountain and amazing vista at the end. $14.40. Best known as the site of the historic 1980 volcanic eruption, the Monument offers a variety of recreation opportunities, including the chance to climb to the summit of the most active volcano in the Cascade Range. Prior to 1980, Mount St. Helens had the shape of a conical, youthful volcano sometimes referred to as the Mount Fuji of America. Mount St. Helens is a popular climb for both beginning and experienced mountaineers. Featuring Mount St. Helens Emerald Jewelry (Obsidianite, Helenite) The Stone: On May 18, 1980 Mount Saint Helen's erupted with the explosive force of 500 Open 7 days a week mid-April through October. Johnston Ridge Observatory - m.p. Nice boardwalk around lake area (easy walk