Another 7,700 homes were under pre-evacuation orders, giving residents time to pack essential belongings and get ready to go at a moment's notice, officials said.
The massive, unpredictable Beaver Creek fire burned swiftly through the Sawtooth National Forest's sage and pine trees, aiming at the resort areas of Hailey and Ketchum, near Sun Valley.
More than 1,100 state and federal firefighters battled the inferno, designated the nation's No. 1 fire priority.
The fire was reported only 8 percent contained early Tuesday.
Some residents of Ketchum and Sun Valley received permission to return home Monday.
In the small mountain town of Atlanta, in the Boise National Forest about 50 miles west of the Beaver Creek fire, Fire Chief Gene Haught said he needed some residents to stay behind, even though all 70 homes were under a forced mandatory evacuation because of the approaching Little Queens fire, which devoured 10,000 acres.
"The fire chief wants all the able-bodied citizens to stay and help him run the hoses to protect the main street," Atlanta resident Amy O'Brien told the Idaho Statesman of Boise.
About 20 of the town's 300 residents stayed behind, O'Brien said, listing herself among the 20.