The Pioneer Historic Byway passes places tied to early Mormon settlement, the Oregon Trail, irrigation, geologic upheaval, conflict, and wildlife in southeastern Idaho. Chesterfield, established in 1879, is an early Mormon settlement on the Oregon Trail with 23 historic brick buildings built between 1884 and 1904, including the old Chesterfield store, and it is listed on the National Register of Historic Places. The Last Chance Canal diverted Bear River water to irrigate Grace Valley and, completed in the early 1900’s, was an engineering masterpiece for its time; without the region’s canal network, farming would not exist there. At Red Rock Pass, about 14,500 years ago, an earthen dam suddenly broke and unleashed one of the largest floods in geologic history as ancient Lake Bonneville, larger than Lake Michigan, emptied in a catastrophic torrent, leaving visible flood evidence such as melon size gravel; today, only the Great Salt Lake in Utah remains of Lake Bonneville. Preston, the seat of Franklin County, was established in 1886 and grew from early Mormon pioneer settlement; the Oneida Stake Academy, built during 1895, is the oldest surviving LDS Church-sponsored education building. Franklin, settled in 1860 by Mormon pioneers, is Idaho’s oldest town and the southern gateway to the byway, with a historic district containing numerous National Register properties and the Relic Hall Museum displaying artifacts from early Mormon settlers. Soda Springs was an Oregon Trail landmark known for its mineral springs and also has the world’s only captive geyser, released on November 30, 1937, when a well driller searching for hot water for a local swimming pool struck the natural geyser at a depth of 317 feet. The Bear River Massacre Site, a National Historic Landmark, was the scene on January 29, 1863, of the largest massacre of Native Americans by U.S. troops west of the Mississippi, when nearly 450 Shoshone men, women, and children camped along the Bear River were attacked and as many as 380 perished. Grays Lake National Wildlife Refuge, where at least 163 bird species live, including the Great Basin Canada Goose and the Sandhill Crane, set aside 19,000 acres in 1965 as a national wildlife refuge and remains a prime place to view Idaho wildlife. At Sheep Rock, early pioneers reached the first division of the Oregon and California Trails, where the Hudspeth Cutoff went west to California and the main Oregon Trail continued northwest to Fort Hall.