Big Slide Mountain takes its name from two dramatic landslides that scarred its southern face in 1830 and 1856, leaving a broad swath of exposed rock visible from Keene Valley far below. At 4,240 feet, it ranks 27th among the Adirondack High Peaks and sits at the head of Johns Brook Valley, flanked by the Great Range to the south and Yard Mountain to the north.
The most popular approach follows The Brothers trail from the Garden parking lot on Route 73 in Keene Valley, a 4-mile route gaining about 2,800 feet. Three rocky crags, the First, Second, and Third Brothers, provide a succession of open lookouts over Keene Valley and the High Peaks before the trail drops briefly into a col and then steepens to the summit. A quieter alternative ascends via the Slide Mountain Brook Trail from Johns Brook Valley, 5.6 miles total from the Garden with roughly 2,000 feet of gain. A third option combines Big Slide with nearby Yard Mountain via the Klondike Notch Trail for a longer, less-traveled circuit.
The open summit rewards with sweeping views across the Great Range, Giant Mountain, and Algonquin Peak. The Garden parking lot fills early on summer and fall weekends, so a weekday or early-morning start is worth planning for. Ice and snow linger on the upper trail well into May, and the exposed rock of the Brothers calls for care in wet conditions.
