Longhorn Valley was a valley along the western ridge of the Highland Mountains on Reach. It was within the Military Wilderness Training Preserve. It was a sloped region ten kilometers across that contained a thick forest of Douglas firs and trampled fields. The Big Horn River ran through the middle of the valley.
On July 23rd, 2552, the night of the initial Covenant incursion, the UNSC Army fireteam 3 Charlie was on patrol in the valley. They were then sent to investigate a disturbance at the Visegrad Relay.
During the Fall of Reach on August 30th, the valley was occupied by the Covenant, who built large defensive encampments in preparation for excavating the Forerunner complex beneath Menachite Mountain. The valley was scorched when a team of SPARTANs used a Fury Tactical Nuclear Weapon to destroy a Covenant cruiser that was holding position overhead. The valley was presumably glassed.
List of appearances
- Halo: The Fall of Reach (First appearance)
- Halo: First Strike
- Halo: Reach
- Halo: Fall of Reach
- Halo: The Fall of Reach - The Animated Series
- Halo: Outpost Discovery (Mentioned only)