The Mackay Dam and Reservoir Site, a water management and recreation area on the East Fork of the Big Lost River, was constructed in the 1930s by the Bureau of Reclamation as part of a larger irrigation project in the area. The approximately 14,000-acre reservoir, stocked with trout and Kokanee salmon, offers boating, fishing, camping, hiking, and wildlife viewing opportunities. RV hookups and tent campsites, a day-use area, and boat launch are all available.

It is located on HW-93, approximately six miles north of Mackay.