The Sphinx Trail earns its place on the Terrifying 25 through a relentless combination of steep, wet terrain, serious scrambling on the upper ledges, and notoriously difficult route-finding. Climbing roughly 1,350 feet in just under a mile, it connects the Great Gulf Trail to Gulfside Trail in the col between Mount Jefferson and Mount Clay, deep within the Great Gulf Wilderness.
Much of the lower trail shadows and repeatedly crosses Sphinx Brook, where wet rock and small, easy-to-miss cairns are the only navigation aids. As a designated wilderness trail, it carries no blazes (a few ancient faded ones survive at odd intervals), and the upper half becomes increasingly hard to follow as cairns thin out and the terrain opens onto steep exposed ledge. A GPS track is essentially required; hikers regularly lose the route near the main brook crossing, where an unobtrusive cairn marks the correct line across.
The upper ledges are steep enough that a slip would be serious, and they drain slowly after rain. Most parties prefer to descend the Sphinx rather than ascend, pairing it as a return from Jefferson after climbing via Six Husbands Trail. The trail lies deep within the Presidential Range's weather shadow, and above-treeline conditions at the Gulfside exit can deteriorate rapidly in any season. Spring and early summer bring high water in Sphinx Brook, making the crossings genuinely risky. Budget extra time regardless; the trail is short but rarely fast.
