Carving the roadbed out of the steep, sheer face of the Garden Wall formation was tricky enough. But in some places, keeping the precariously placed roadbed from eventually falling away from the mountainside was just as troublesome. That particular problem was solved by pinning the road against the mountainside with retaining wall. There are several walls shoring up the road along the Garden Wall, but the greatest number of these retaining walls are located in the sheer cliffs of the rimrock approaching Logan Pass.

Retaining walls are common features in mountain road building. What makes the retaining walls on the Going-to-the-Sun Road unique is the NPS's stipulation that they had to blend in, almost invisibly, with the surrounding landscape. To achieve this, the walls were constructed of native stone gathered up from the cliff excavations along the road. They were also designed to appear massive, in keeping with the heft of the mountains they pressed against. Stonemasons placed boulders as large as they could handle in most of the walls. In some sections, they used a derrick to place the large, unwieldy stones.

The Russian stonemasons who built the retaining walls were superb craftsmen. They constructed two kinds of retaining walls along the road. Some were mortared and some were dry-stacked. All of the walls were carefully stacked with various-sized, uneven stones to make the appear more natural. Where the road passed over waterways or spanned cliff walls that were too difficult to bench, the stonemasons crafted graceful half-arches to provide outlet portals for culverts and small bridges.

-from Chapter Four, "The Impossible Takes a Little Longer"