 At the Colorado River, additional hazards include hypothermia (due to the river's consistently cold temperatures), trauma (due to collisions with boulders in rapids), and drowning.This trail was built in the last decade of the 19th century by horsetheives, but was improved by different prospectors of that era.The Atchison, Topeka and Santa Fe Railway improved the trail further around 1910 to compete with the Camerons' Bright Angel Trail which charged a toll at the time.