1. The Russian-American Company was dissolved on December 31, 1867, thus ending the era of Russian rule in Alaska. This paved the way for the United States to purchase Alaska from Russia the following day.

2. On December 31, 1970, the last operational U.S. military base in Alaska, Fort Richardson, officially transferred control to the U.S. Army. This marked the end of the Cold War military buildup in Alaska.

3. In 1986, the Exxon Valdez oil spill occurred on December 31, when the oil tanker ran aground on Bligh Reef in Prince William Sound, Alaska. This was one of the worst environmental disasters in U.S. history, with millions of gallons of oil spilling into the ocean and causing long-term damage to the ecosystem and wildlife.

4. On December 31, 1999, Alaska became one of the last states in the U.S. to officially recognize Kwanzaa, a week-long celebration of African-American culture and heritage. This recognition was seen as an important step towards promoting diversity and inclusivity in the state.

5. December 31, 2019 marked the end of a decade that saw significant changes in Alaska, including the state's first-ever recreational marijuana shops opening for business, the legalization of same-sex marriage, and increased attention to environmental issues such as climate change and the effects of oil drilling on local communities.