1. Statehood Day: December 31, 1889, was a significant day in North Dakota's history as it was the day when the state was officially admitted into the Union as the 39th state.

2. Blizzard of 1966: On December 31, 1965, a blizzard hit the state of North Dakota, which continued until the next day, causing widespread devastation. The storm led to the death of 74 people, making it one of the deadliest blizzards in North Dakota's history.

3. Great Northern Railway Bridge Collapse: On December 31, 1928, the Great Northern Railway Bridge collapsed over the Rainy River between Minnesota and Canada. The accident caused four deaths and disrupted transportation and commerce in the region for many months.

4. Norwegian Immigration: December 31 is a significant day for Norwegian Americans in North Dakota as it marks the anniversary of the arrival of the first Norwegian immigrants in the state in 1871.

5. Major oil discovery: In 1951, a major oil discovery was made in the state of North Dakota on December 31. The discovery led to the booming of the oil industry in the state, which continues to be a significant contributor to the state's economy.

Overall, December 31 has been a significant day in North Dakota's history, marked by events ranging from statehood to natural disasters, immigration, and major economic discoveries.