A Wonderful Piece of Engineering: The Big Side Cut

Mullan reported his rock cuts along this stretch as fifteen to twenty feet wide, and the rock disagrees. When the surviving Point of Rocks segment near Alberton was surveyed for the National Register, where it was listed in 2009, its cuts averaged about fourteen feet, blasted with black powder, the rubble thrown to the sides rather than hauled away. The Milwaukee Road sliced through the old grade in 1908 and built a short bypass for wagons. This sign repeats, word for word, the one at the Alberton rest area about twelve miles east.

What the plaque says

A Wonderful Piece of Engineering: The Big Side Cut The Mullan Road is carved into the face of the mountains high above the Clark Fork River west of here. Lieutenant John Mullan tried to keep his wagon road as close to the river as possible. But when his work crews ran up against a mountain spur that reached all the way to the edge of the river, he was forced to seek an alternate route. Mullan later wrote that "to make this six-mile cut through rocky spurs was an undertaking that I almost feared to attempt." On May 10, 1860, he assembled his entire work force of 150 citizens and soldiers at the west side of the spur. For the next six weeks, his men dug, whittled, and blasted their way up the mountain side to an altitude of a thousand feet above the river. A premature explosion while clearing a path through the rocks wounded one man and severely stunned another. When completed in June 1860, the Big Side Cut segment was the most awe-inspiring of the entire 624-mile Mullan Road. A traveler wrote of the Big Side Cut in 1862 that it was "a narrow wagon track which left no room for careless or uncertain driving."

Where it stands

Worth the stop nearby

• Ninemile Remount Depot — 17 mi
  The Forest Service's mule ranch, built because the fires of 1929 ran out of packers.

More markers nearby

• Flying High Across the Big Sky — 11 mi
• Glacial Lake Missoula — 12 mi
• A Wonderful Piece of Engineering: The Big Side Cut — 12 mi
• The Natural Pier Bridge — 13 mi