It includes 20 separate tracts of land and covers over 50,000 acres (20,230 ha) that stretch across Fayette, Somerset, and Westmoreland Counties.

[citation needed] The sparks of passing steam locomotives of the Pittsburgh, Westmoreland and Somerset Railroad ignited wildfires that prevented the formation of second growth forests.

The Pennsylvania General Assembly passed a piece of legislation in 1897 that authorized the purchase of "unseated lands for forest reservations."

Several portions of what is now designated as part of the Forbes State Forest had previously been either developed or commercially exploited through logging through the early-to-mid-20th century.

After previous development and logging, this portion of the west slope of Laurel Ridge is currently undergoing reforestation.

Frost causing the patches to be pushed up higher than their surroundings is followed by the effects of natural erosion which results in stones sliding to the bottom of the protrusion and forming ring-like patterns at the base.Spruce Flats Wildlife Management Area covers 305 acres (123 ha), with a focal point on the 28 acres (11 ha) of the Spruce Flats Bog which formed in a natural depression atop Laurel Ridge.

The bog currently hosts a large community of cranberry, pitcher plant, sundew, and cotton grass.