In the 1800s, Alaska did not have a road system. In summers, people used boats to travel along coasts, rivers and lakes. In winter Alaskans used sleds pulled by dogs (huskies) to travel through the land that was covered in deep snow. Dog sleds were used as a mode of transportation to carry mail, people, supplies and gold. Some routes were preferred and they formed trails.
In the 1920s airplanes started being used for transport and in the mid 1900s snow machines became very popular. This changed the traditional mode of transportation in Alaska.
These days dog sledding is primarily a sport and is not used as a means for travel.