Pine Mountain is set approximately 40 miles (64 km) northeast of downtown Los Angeles within San Gabriel Mountains National Monument and the Sheep Mountain Wilderness. It ranks as the second-highest peak in the San Gabriel Mountains, second-highest in the wilderness and monument, and the 10th-highest in the county. Topographic relief is significant as the summit rises 2,650 feet (808 meters) above North Fork Lytle Creek in approximately one mile (1.6 km). Reaching the summit involves 6.5 miles of trail hiking with 1,600 feet of elevation gain. The mountain was named by the US Forest Service for the dense stand of Jeffrey Pine and white fir covering the slopes. This landform's toponym has been officially adopted by the U.S. Board on Geographic Names and first appeared in 1901.

According to the Köppen climate classification system, Pine Mountain is located in a continental climate zone (Dsa) with mostly dry summers (except for scattered summer thunderstorms) and cold, wet winters. Most weather fronts originating in the Pacific Ocean travel east toward the San Gabriel Mountains. As fronts approach, they are forced upward by the peaks (orographic lift), causing them to drop their moisture onto the range. Precipitation runoff from this mountain's west slopes drains to the San Gabriel River and the east slope drains into Lytle Creek.

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