Upper Sam Merrill Trail and Idlehour Trail

The Upper Sam Merrill Trail and Idlehour Trail is a 23.8 km trail that starts in Altadena, Los Angeles County, California. Based on our data, the hike is graded as Difficult. For information on how we grade trails, please read measuring the difficulty of a hiking trail on hiiker. Also, check our latest community posts for trail updates. This hike can be completed in approx 6 hrs 54 mins. Caution is advised on trail times as this depends on multiple variables. For more info read about how we calculate hike time.