Restart

After the dogs are shuttled to the third checkpoint, the race restarts the next day (Sunday) at 2:00 p.m. AST. Prior to 2004, the race was restarted at 10:00 a.m., but the time has been moved back so the dogs will be starting in colder weather, and the first mushers arrive at Skwentna well after dark, which reduces the crowds of fans who fly into the checkpoint.

The traditional restart location is the headquarters of the Iditarod Trail Committee, in Wasilla, but warm weather and poor trail conditions can push the restart further north to Willow Lake, and in 2003 it was bumped 300 miles (500 km) north to Fairbanks. The mushers depart, separated by the same intervals as their arrival at the second checkpoint.

The first 100 miles (160 km) from Wasilla through the checkpoints at Knik, and Yetna Station, to Skwentna are known as "moose alley". The many moose in the area find it difficult to move and forage for food when the ground is thick with snow. As a result, the moose sometimes prefer to use pre-existing trails, causing hazards for the dog teams. In 1985, Susan Butcher lost her chance at becoming the first woman to win the Iditarod when her team made a sharp turn, and encountered a pregnant moose. The moose killed two dogs and seriously injured six more in the twenty minutes before Duane "Dewey" Halverson arrived and shot the moose. In 1982, Dick Mackey, Warner Vent, Jerry Austin, and their teams were driven into the forest by a charging moose.

Otherwise, the route to Skwentna is easy, over flat lowlands, and well marked by stakes or tripods with reflectors or flags. Most mushers push through the night, and the first teams usually arrive at Skwentna before dawn. Skwentna is a 40-minute hop from Anchorage by air, and dozens of planes land on the airstrip or on the Skwentna River, bringing journalists, photographers, and spectators.

From Skwentna, the route follows the Skwentna River into the southern part of the Alaska Range to Finger Lake. The stretch from Finger Lake to Rainy Pass, on Puntilla Lake, becomes more difficult, as the teams follow the narrow Happy River Gorge, where the trail balances on the side of a heavily forested incline. Rainy Pass is the most dangerous check point in the Iditarod. In 1985, Jerry Austin broke a hand and two of his dogs were injured when the sled went out of control and hit a stand of trees. Many others have suffered from this dangerous checkpoint. Rainy Pass is part of the Historic Iditarod Trail, but until 1976 the pass was inaccessible and route detoured through Ptarmigan Pass, also known as Hellsgate, because of the 1964 Good Friday Earthquake.