Various breeds used in dog sledding today
Dog sledding still exists today, though now it is mostly a sport, as opposed to being a form of necessary transportation, like in the Balto movies (ie carrrying the mail). There are several types of sled dog events, and some breeds are better suited to some events than others.
NOTE: There are actually almost endless forms of "sled dogs." Anything with the desire and weight to safely pull (At least 30 pounds or so in body weight) can be a sled dog with or without snow (without snow is called "dryland" mushing). For example. I have a 50 lb lab/chow/pit mix that was a rescue dog. She was my started sled dog (we tried, failed, learned, and succeded together) and is still one of my most reliable leaders at 8/9 years old. Her only glitch is she's not built well and isn't as fast/enduring as racing sled dogs. So, point being, this list certainly won't be complete, but these are the most commonly used dogs in racing today.
Alaskan Huskies: A popular choice these days, generally being some of the fastest. This is not a real "breed" of dog, but is rather a glorified mutt. Breeders will put various breeds together to create the fastest, strongest dog, with the best appetite, the best body form, and the toughest feet. Alaskan huskies might have some Siberian husky, some German Shorthair Pointer, some Saluki, etc. Anything goes. Looks and AKC/CKC/etc certification is not usually a super competetive musher's first thought when it comes to choosing his/her team. Alaskan huskies of course have no "breed" standards, as they aren't a real breed and can look like anything. They have an extremely strong desire to pull and have been the champions of numerous sprint, mid-distance, and distance races in recent times. Just recently, Lance Makey completed both the Yukon Quest and the Iditarod back to back with his Alaskan Husky team, placing first in both races (several years in a row). Similarly, Blayne Streeper placed first in the Fur Rendevous, a huge sprint race, in Anchorage, AK with Alaskan Huskies. Here are some examples:
Images from Lance Makey's Comeback Kennel webpage and http://www.dogtec.com/kennel/streeper-kennels/dog/sleemam
Siberian Huskies: These dogs were originally from (surprise) Siberia. They were brought over to Alaska by fur traders. In 1909, William Goosak (a fur trader that brought some Siberians to Nome) almost won the All Alaska Sweepstakes in it's second running. In 1915, Leonhard Seppala won the Sweepstakes with his team of Siberians. After that, Seppala continued to dominate the race. Seppala and his Siberians were also a part of the relay to Nome in the 1925 diptheria serum run, traveling 340 miles (most teams in the relay ran less than 50 or so). Since then Siberians have been recognized by the AKC and other organizations. Siberian huskies come in two varieties: Show lines and racing lines. Show lines were developed to meet the breed standards set by the AKC and include the red/white coloration. Show Siberians tend to be a little shorter with fluffier coats and long, curved tails carried over the back. Racing lines were mainted to produce the fastest and strongest working dogs. The red coloration is generally absent in the best working lines. Racing dogs tend to be leggier (taller) and don't always have the classic "mask" as is seen in show lines (some do, but blazes and other markings are common). Both lines come with blue or brown eyes, or a mixture of the two. Siberians also can run sprint, mid, or long distance races. They provide a little more power than many Alaskan Huskies. Here are some examples:
Images from Tumnatkisiberians.com (the dogs are Mishap and Fisbo) and http://www.pokusiberians.com/473/index.html
Malamutes: Malamutes can be used for racing today, but they are never really "competitive." Siberians and Alaskans are the ones that place in sprint/mid/long distance races. Malamutes do however, compete in competitions called "weight pulls." This type of competition is divided into weight classes. In each class, the competition is to see which dog can pull the most weight. Malamutes' strong and powerful builds make them ideal for these competitions, as well as for freight sledding (hauling heavy loads in teams over short distances), which are a type of race. The Malamute's build and weight give them the power to participate in those type of competitions. They tend to have a steady, but slower gait that they can maintain for long distances. Here are some examples:
Images from http://www.cascademalamutes.com/ and http://www.quinault.net/
Samoyeds: Samoyeds are also still used for racing today, though, like the Malamutes, their size and pacing makes them less competitive in sprint/mid/long distance racing. These are large, very fluffy white dogs. I'm unsure as to if they compete frequently in things like freight races and weight pulls, but I do know they compete in sprint/mid- distance races (and occasionally long distance). They have a slower, but steady pace, similar to the Malamute. They are an AKC recognized breed. This is a breed I'm less familiar with, so I'm not sure if they too, like the Siberians, have a split in lines (race vs show). I do know many racing Samoyeds also show in the ring. Because of that, one might guess that there is a lack of difference between show/race dogs. Here are some examples:
All images from http://home.earthlink.net/~dashinsam/index.html
There are plenty of other breeds that were bred to pull. Some others you can look up include: Canadian Eskimo Dog, Chinooks, Inuit Sled Dog, Mackenzie River Huskies, and Greenland Dogs. Many native/tribal dogs from northern areas are/were used for sledding. The ones I listed and described here are the most commonly seen in the racing community today.
Personally, I race and train with a Siberian Husky sled dog kennel, so I am the most informed about them. I am aware that the information I gave is minimal and incomplete. If you're interested in breed standards, feel free to look them up via the American Kennel Club (or other organizations).
I hope this has been informative and interesting to those interested in the real story behind sled dogs. Depending on the interest generated by this article, more about dog mushing may be written.