Mackay Reservoir, reservoir on the Big Lost River in Custer County, Idaho, United States
Mackay Reservoir is a large body of water in Idaho's high desert, created by a dam built in 1918 on the Big Lost River and stretching across more than 1,300 acres. The water sits surrounded by mountains, with calm surfaces that attract both shore and boat fishing, and the landscape features open terrain with recreation access points along the shoreline.
The dam was constructed in 1918 to support irrigation in the valley and stands about 67 feet tall. Mackay purchased the facility in 1936, after which it became central to local identity and has withstood significant challenges including a major earthquake in 1983 that tested its structural integrity.
Mackay Reservoir is a gathering place where fishing is the main draw for both locals and visitors seeking to spend time outdoors. The simple rhythm of casting lines and watching the water connects people to the landscape and to each other in a quiet, unhurried way.
The reservoir is about 5 miles north of Mackay town, easily accessible from Highway 93 without a long drive. Visitors can fish from shore or bring boats, access restrooms and designated recreation areas, and should bring proper safety gear and warm clothing for winter ice fishing when conditions allow.
The reservoir comes alive on Independence Day when the towns of Mackay and Arco host a fireworks display that lights up the night sky above the water. This shared community tradition draws locals and visitors together to celebrate in a place normally known for quiet reflection.
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