History of Three Island Crossing State Park

Oregon Trail pioneers knew Three Island Crossing well. It was one of the most famous river crossings on the historic trail and the most difficult crossing in Idaho. Crossing the Snake River was always dangerous, but when the water was low enough to negotiate, everyone crossed who could, to take advantage of the more favorable northern route to Fort Boise. During high water, most emigrants were forced to travel along the South Alternate route into Oregon — a dry, sandy, dusty, and hot trail that wore out man and beast.

The original course of the Oregon Trail was from Independence, Missouri to Oregon City in Oregon’s Willamette Valley. Most pioneers traveled the trail from 1841 through 1848. However, fur trappers and explorers used the travel corridor as early as 1811. By the mid-1860s, the trail was used little as an emigration route. 

The Oregon Trail entered Idaho in the southeast corner of the state. At Fort Hall, it joined the Snake River, following the south bank until Three Island Crossing was reached near Glenns Ferry. The route left Idaho near the site of old Fort Boise, near Parma, after winding through 500 miles of the state. 

Upon reaching the Three Island Ford, the emigrants had a difficult decision to make. Should they risk the dangerous crossing of the Snake, or endure the dry, rocky route along the south bank of the river? About half of the emigrants chose to attempt the crossing by using the gravel bars that extended across the river. Not all were successful; many casualties are recounted in pioneer diaries. The rewards of a successful crossing were a shorter route, more potable water and better feed for the stock.

The Three Island Ford was used by pioneer travelers until 1869, when Gus Glenn constructed a ferry about two miles upstream. Some travelers continued to cross at Three Island to avoid paying for the ferry.