1) On May 18, 1980, Mount St. Helens in Washington state erupted, sending ash and debris into the atmosphere. While Alaska was not directly impacted by the eruption, the ash cloud eventually spread over the state and resulted in airline cancellations and disruptions in air traffic.

2) On May 18, 1925, the infamous serum run to Nome officially ended when a train carrying the much-needed diphtheria antitoxin arrived in the city. The dogsled relay race had covered over 674 miles in just five and a half days, saving many lives in the process.

3) May 18, 1867 marks the day when the Russian Empire officially sold Alaska to the United States for $7.2 million dollars in a deal known as the Alaska Purchase. The acquisition of this vast land area changed the course of Alaska's history and helped shape its identity as the 49th state of the U.S.

4) In 1972, a powerful earthquake struck the Aleutian Islands on May 18, registering a magnitude of 6.9 on the Richter scale. The quake caused significant damage to infrastructure in the remote region, including ruptured gas lines and damage to buildings.

5) On May 18, 1986, Alaska Airlines Flight 68 crashed near Ketchikan, killing all 111 people on board. The cause of the crash was determined to be a mechanical failure, leading to new regulations and safety measures in the aviation industry.