1. Statehood Day: On September 15, 1889, North Dakota officially became a state, along with South Dakota. This day is celebrated annually as Statehood Day in North Dakota.

2. Devil's Lake: On September 15, 1890, the U.S. Army established Fort Totten near Devil's Lake, North Dakota, as part of their efforts to control the region after the defeat of Sitting Bull.

3. Fargo Tornado: On September 15, 1957, a devastating tornado struck Fargo, North Dakota, and Moorhead, Minnesota, causing widespread damage and killing 10 people. It remains the deadliest tornado in North Dakota history.

4. UND Integration: On September 15, 1954, the University of North Dakota officially became the first university in the United States to integrate its student body, following a legal battle over the admission of Native American students.

5. Teddy Roosevelt: On September 15, 1883, future U.S. president Theodore Roosevelt embarked on his first hunting trip to North Dakota, which would inspire his lifelong passion for conservation and his advocacy for national parks.