Lots of birds, frogs and other wildlife. 52 OPEN Mid-May thru Mid-Oct. See them … Over 230 square miles of … We were there on a Tuesday and it was closed so check when it’s open before you go. Johnston Ridge Observatory - m.p. And because it is an active volcano, it is best not to put it off for too long. 33 - Exhibits Open May 18-Sept 8, 10AM-4PM DAILY. WHAT IS OPEN OR CLOSED AT MOUNT ST HELENS? Harry's Ridge is a great hike, about 10 miles roundtrip from the main parking area. 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 Lots of views of the mountain and amazing vista at the end. Nice boardwalk around lake area (easy walk