was in use by the operators of the Spokane, Portland and Seattle Railway Company in the early 1900s to guard against rockfalls spilling onto the tracks and causing an accident. A series of electrified wires were strung along the more unstable sections of the rock cuts in the columnar basalts that are prone to toppling. Should the circuit be cut it would potentially indicate that a rock had severed the wire. Some relics of this system remain along the paved trail in the form of standing poles, some with insulators. The line was abandoned by the railroad in 1987 and eventually incorporated into the Columbia Plateau State Park Trail.
Location of a recent rockfall onto the paved trail. The vertical spacing of the insulators suggests a series of parallel wires, strung pole to pole, along the length of a cut.
