They delivered the medicine in only 27.5 hours. This historic event is commemorated with the world famous Iditarod Sled Dog Race . The Nenana Ice Classic The Nenana Ice Classic administration provides yearly short-term employment for nearly 100 locals. Alaskans wager thousands of dollars yearly on the day and time of the break up of the Tanana River. Large grooves are cut into the frozen Tanana River ice about 300 feet from shore.
Volunteers lends their muscles to pull on ropes to stand a wooden tripod upright.
Holes are drilled in the ice, allowing water to seep upwards, filling in the grooves to freeze the tripod in place. Once the ice has thawed to the point where walking on it is no longer safe, a wire is attached from the watchtower on shore to the top of the tripod, and rigged up to a clock mechanism so that the clock will be stopped when the tripod moves 100 feet. Watchmen monitor from the time the clock is activated until the ice has gone out. A siren will alert the townspeople to the tripod's first movement. When the tripod trips the clock, spring has officially arrived, and Interior Alaska's rivers are once more navigable.