Island Park is actually the world's largest crater, 23 miles in diameter, created from a volcano which collapsed in prehistoric times. Now covered in a dense forest of pine and wildflowers, it is a mecca for hiking and fishing in summer and cross-country skiing and snowmobiling in winter. Island Park Reservoir and Henry's Lake are popular for fishing summer and winter.

     The city of Island Park boasts of the longest main street in America at 33 miles in length, extending from Valley View to Last Chance. Although long, there are miles of forest service land with no development along this main street. Every few miles we come to a small settlement with some business and homes.

     Valley View, the north end of Island Park, is located 7 miles west of where we are camped.

     Big Springs is located where the 1.3 million year old Henry's Fork Caldera is covered by the western edge of the more recent Buffalo Lake lava flow, which erupted from vents on the Yellowstone Plateau to the east. Geologist believe that the main source of the springs is the rain and snow that falls on the Yellowstone Plateau. This water percolates through the highly fractured lava until it meets less permeable glacial and lake sediments beneath the lava. This causes the water to spread laterally, emerging at the base of the Plateau as Big Springs, the largest of many springs that emerge along the western edge of the Yellowstone Plateau. Thermal waters from deeeper sources may contribute to the springs' flow and account for its year round temperature of 52 degrees.

     Big Springs is the headwater for the Henry's Fork of the Snake River. It flows at 150 million gallons per day of pure, clean water.

     Johnny Sack was a craftsman and a German immigrant who finished building his cabin and water wheel from native lumber and rock in 1935. He was not a big man, and stood less than five feet tall, so he built the cabin and his furniture to to fit his height. Along side the cabin stands a unique, working water wheel to supply electricity and pump water to the cabin.

     Henry's Fork of the Snake River was named for Andrew Henry, who led a trapping expedition through the area in 1810.

     The Mesa Falls Scenic Byway is 29 miles long, extending from Ashton, ID to Island Park. Leaving Big Springs, we traveled south to Ashton to pick up this scenic route. Traveling north once again following the Henry's Fork River. We pass the turnoff for Cave Falls in YNP, and make a note to return and visit this hidden corner of Yellowstone. This byway is a beautiful drive, with vistas to die for. We love our Rocky Mountains.

     Soon we come to the rim of the caldera, where the river tumbles down the lava flows creating two beautiful falls. Upper Mesa Falls at 114 feet high and 200 feet wide and Lower Mesa Falls at 65 feet high are the only remaining undisturbed major falls in the Columbia River System.