The start of the first race in 1973

Frequently teams race through blizzards causing whiteout conditions, and sub-zero weather and gale-force winds which can cause the wind chill to reach -100 °F (-75 °C). The trail runs through the U.S. state of Alaska. A ceremonial start occurs in the city of Anchorage and is followed by the official restart in Wasilla, a city in the south central region of the state. The trail proceeds from Wasilla up the Rainy Pass of the Alaska Range into the sparsely populated interior, and then along the shore of the Bering Sea, finally reaching Nome in western Alaska. The teams cross a harsh but starkly beautiful landscape under the canopy of the Northern Lights, through tundra and spruce forests, over hills and mountain passes, and across rivers. While the start in Anchorage is in the middle of a large urban center, most of the route passes through widely separated towns and villages, and small Athabaskan and Inuit settlements. The Iditarod is regarded as a symbolic link to the early history of the state, and is connected to many traditions commemorating the legacy of dog mushing.

The race is the most popular sporting event in Alaska, and the top mushers and their teams of dogs are local celebrities; this popularity is credited with the resurgence of recreational mushing in the state since the 1970s. While the yearly field of more than fifty mushers and about a thousand dogs is still largely Alaskan, competitors from fourteen countries have completed the event including the Swiss Martin Buser, who became the first international winner in 1992.

The Iditarod received more attention outside of the state after the 1985 victory of Libby Riddles, a long shot who became the first woman to win the race. Susan Butcher became the second woman to win the race, and went on to dominate for half a decade. Print and television journalists and crowds of spectators attend the start at the intersection of Fourth Avenue and D Streets in Anchorage, and in smaller numbers at the checkpoints along the trail.

Portions of the Iditarod Trail were used by the Native American Inuit and Athabaskan peoples hundreds of years before the arrival of Russian fur traders in the 1800s, but the trail reached its peak between the late 1880s and the mid 1920s as miners arrived to dig coal and later gold, especially after the Alaska gold rushes at Nome in 1898, and at the "Inland Empire" along the Kuskokwim Mountains between the Yukon and Kuskokwim rivers, in 1908.

The primary communication and transportation link to the rest of the world during the summer was the steamship; but between October and June the northern ports like Nome became icebound, and dog sleds delivered mail, firewood, mining equipment, gold ore, food, furs, priests, and other needed supplies between the trading posts and settlements across the Interior and along the western coast. Roadhouses where travelers could spend the night sprang up every 14 to 30 miles (23 to 48 km) until the end of the 1920s, when the mail carriers were replaced by bush pilots flying small aircraft and the roadhouses vanished. Dog sledding persisted in the rural parts of Alaska, but was almost driven into extinction by the spread of snowmobiles in the 1960s.

The Iditarod was the brainchild of Dorothy G. Page (the "Mother of the Iditarod"), who wanted to sponsor a sled dog race to honor mushers. With the support of Joe Redington, Sr. (the "Father of the Iditarod"), the first race (then known as the Iditarod Trail Seppala Memorial Race in honor of Leonhard Seppala) was held in 1967 and covered 25 miles (40 km) near Anchorage. The purse of USD $25,000 attracted a field of 58 racers, and the winner was Isaac Okleasik. The next race, in 1968, was canceled for lack of snow, and the small $1,000 purse in 1969 only drew 12 mushers.

Redington was the impetus behind extending the race more than 1,000 miles along the historic route to Nome, and a major fundraising campaign which raised a purse of $51,000. The first true Iditarod was held in 1973, and attracted a field of 34 mushers, 22 of whom completed the race. The event was a success; even though the purse dropped in the 1974 race, the popularity caused the field of mushers to rise to 44, and corporate sponsorship in 1975 put the race on secure financial footing. Despite the loss of sponsors during a dog abuse scandal in 1976, the Iditarod caused a resurgence of recreational mushing in the 1970s, and has continued to grow until it is now the largest sporting event in the state. While the race was originally patterned after the All Alaska Sweepstakes, the Iditarod Trail Committee promotes it as a commemoration of the serum delivery.
 
The race's namesake is the Iditarod Trail, which was designated as one of the first four National Historic Trails in 1978. The trail in turn is named for the town of Iditarod, which was an Athabaskan village before becoming the center of the Inland Empire's Iditarod Mining District in 1910, and then turning into a ghost town at the end of the local gold rush. The name Iditarod may be derived from the Athabaskan haiditarod, meaning "far distant place".

The main route of the Iditarod trail extends 938 miles (1,500 km) from Seward in the south to Nome in the northwest, and was first surveyed by Walter Goodwin in 1908, and then cleared and marked by the Alaska Road Commission in 1910 and 1911. The entire network of branching paths covers a total of 2,450 miles (3,945 km). Except for the start in Anchorage, the modern race follows parts of the historic trail.

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