The Birkie is one of the few races worldwide that is named after and commemorates a historical episode - in this case an episode from 1206 when a group of Birkebeiners - soldiers who fought for Sverre Sigurdsson and his descendants in the Norwegian civil war - smuggled the illegitimate son of Norway's King Håkon Sverresson from Lillehammer to safety in Trondheim. At Birkebeinerrennet in Norway, skiers still carry packs symbolizing the weight of an 18-month-old child; this tradition, although not required, is also respected by some skiers in the American Birkebeiner.
The Birkie course is quite hilly, and is recognized as one of the more difficult cross country ski marathon courses in the world. The current north-south alignment (used since 1992) has skiers traversing a 2-km flat section before turning up "Powerline Hill", a series of climbs to the 4.5-km mark. The trail then rolls until 12-km, when Firetower Hill takes competitors to 1730 feet (527 meters), the high point of the race and a climb of nearly 400 feet (122 meters) from the race start. In early years of the race, the Birkie began with a climb up the alpine slopes of Mount Telemark, but larger field sizes made this impractical. It was done mainly as a publicity stunt. Beyond High Point is a series of downhills, including "Bobblehead Hill" or "Sledder Hill" which has a rather tricky downhill, right turn near a snowmobile trail — allowing dozens of snowmobilers to watch and "score" skiers' falls. The trail rises steeply to the crossing of County Road OO (Referred to as "Double-Oh" which, at 22.8-km, is the unofficial halfway point of the race. Until 2001, the 23-km Korteloppet race ended here but has since been rerouted back to Telemark after splitting off from the main course at 9-km.
Beyond OO the course is less hilly, but by no means flat. After 40-km is the aptly named "Bitch Hill" where spectators cheer skiers up the steepest climb of the race. Several kilometers later (just south of Highway 77) is the last lengthy ascent of the race- El Moco- known for its numerous bends; each offering the empty promise of a summit. From the top, Hayward's watertower is a most welcome sight. There are several road crossings and open fields before the course empties onto Lake Hayward. Warm conditions have occasionally required the finish line be moved to a flat field just west of the lake. The four kilometer crossing of the lake is obviously flat, but unprotected from wind. Once off the lake the trail twists through the outskirts of Hayward on snow trucked in for the event. Over the course of hours thousands of tired and proud skiers make their way past three blocks of cheering spectators lining Hayward's Main Street.
The race begins with several waves in order to thin skiers out along the course. The first wave is made up of Elite skiers (generally around 200) who depart Cable at 8:20 AM, followed by Elite Women at 8:22. Waves then depart every ten minutes until the tenth and final wave leaves at 10:00 AM. New skiers must ski in Wave 10 unless they use another ski marathon time to qualify up to Wave 3. Waves 2 and 1 are open only to skiers who have skied in previous Birkies. The 23-km Korteloppet starts with the Birkie and Korte skiers are mixed in with the Birkie waves, distinguished by their yellow bibs.