Alaska is marking 140 years since it was sold to the United States. Every year residents in the city of Sitka raise a Russian Imperial flag to remember when 1.5 million kilometres of vast mountain ranges, untouched wilderness, and natural resources were o

In the north-west of the U.S. the official motto of Alaska Day is 'Sawdust and Ice' – commemorating Russian settlers who sold ice to Americans carrying it in boxes with sawdust which was preventing it from melting.

The first European contact with Alaska took place in 1741, when Vitus Bering led an expedition for the Russian Navy aboard the St. Peter.

Iditarod Trail Sled Dog Race, Alaska

The area was considered to have the finest fur in the world and the first permanent European settlement was founded there in 1784, but Russia never fully colonised it.

The United States purchased Alaska from the Russian Empire for $US 7.2 million in 1867. Each acre cost just two cents – the price of around one kilogram of corn at the time.

But even then many Americans thought the government had overpaid for this remote and unsettled territory – until 30 years later adventurers found gold there, and later large deposits of oil and gas worth hundreds of billions of dollars.

Alaska became the 49th U.S. state in 1959 and now accounts for half of the country's oil, coal and precious metals deposits.

It's the largest American State, with the third largest annual average income per person.