They are home to the world's largest organism and fungal mycelial mat, the Armillaria solidipes.
The Blue Mountains are uplift mountains in how they were formed.
Geologically, the range is a part of the larger rugged Columbia River Plateau, located in the dry area of Oregon east of the Cascade Range. The highest peaks in the range include the Elkhorn Mountains at 9,108 feet,
Strawberry Mountain at 9,038 feet, and Mount Ireland at 8,304 feet. The nearby Wallowa Mountains, east of the main range near the Snake River, are sometimes included as a subrange of the Blue Mountains.
Historically, the river valleys and lower levels of the range were occupied by indigenous peoples for thousands of years. Historic tribes of the region included the Walla Walla, Cayuse people and Umatilla, now acting together as the Confederated Tribes of the Umatilla Indian Reservation, located mostly in Umatilla County, Oregon.
In the middle 19th century, the Blue Mountains were a formidable obstacle to settlers traveling on the Oregon Trail and were often the last mountain range American pioneers had to cross before reaching either southeast Washington near Walla Walla or passing down the Columbia River Gorge to the end of the Oregon Trail in the Willamette Valley near Oregon City.
The range today is traversed by Interstate 84, which crosses the crest of the range at a 4,193 feet summit, from south-southeast to north-northwest between La Grande and Pendleton. The community of Baker City is located along the south-eastern flank of the range. U.S. Route 26 crosses the southern portion of the range, reaching a summit of 5,098 feet at Blue Mountain Pass.