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An 11.25 miles round trip that gains 4300 feet of elevation. Plan for seven hours to complete this strenuous hike. The trail is in good condition with some difficult spots.
Henninger Flats is a small hanging basin 2600 ft above sea level in the San Gabriel Mountains in the Angeles National Forest. It was part of the Mount Wilson Toll Road. The trailhead to reach the flats is at the top end of Eaton Canyon in Altadena.