Glenns Ferry is a city in Elmore County, Idaho, United States. The population was 1,611 at the 2000 census. The city is adjacent to Interstate 84 and the Snake River. Glenns Ferry was one of the most famous river crossings on the Oregon Trail. Pioneers forded the Snake River at the Three Island Crossing until 1869, when Gustavus "Gus" Glenn constructed a ferry about two miles upstream, primarily to expedite freight but also for emigrants. His boat, which could hold two wagons, cut nearly twenty miles from the former route. Three Island Crossing State Park, opened in 1971, is home to The Oregon Trail History and Education Center, where visitors can learn about pioneer emigrants and Native American history. The Glenns Ferry community sponsors a crossing commemoration the second Saturday of each August. The townsite was platted in 1871, just downstream from the ferry site, and the first bridge across the Snake River was built here in 1908.