Whitehorse is the capital and largest city of Yukon, Canada and the largest city in northern Canada. It was incorporated in 1950 and is located at kilometre 1426 on the Alaska Highway in southern Yukon. Whitehorse's downtown and Riverdale areas occupy both shores of the Yukon River, which originates in British Columbia and meets the Bering Sea in Alaska. The city was named after the White Horse Rapids for their resemblance to the mane of a white horse, near Miles Canyon, before the river was dammed. Because of the city's location in the Whitehorse valley, the climate is milder than other comparable northern communities such as Yellowknife. At this latitude winter days are short and summer days have 20 hours of daylight. The town of Whitehorse, as reported by the Guinness World Records, is the city with the least air pollution in the world.