1. Idaho became a U.S. territory on March 3, 1863: March 3, 1863 is a significant date in Idaho history as it marks the establishment of the Idaho Territory. The territory was created by the United States Congress and was carved out of the Washington Territory.

2. The first capital of Idaho was Lewiston: Shortly after the establishment of the Idaho Territory, the city of Lewiston was chosen as its capital. Lewiston served as the capital until 1865 when it was moved to Boise.

3. The Idaho State Capitol building was completed on March 3, 1920: The Idaho State Capitol building in Boise is a significant landmark in the state's history. It was completed on March 3, 1920, and has been the seat of Idaho's government ever since.

4. Idaho celebrated its centennial on March 3, 1990: March 3, 1990, marked the 100-year anniversary of Idaho's statehood. To commemorate the occasion, the state held a variety of events and celebrations throughout the year.

5. March 3 is National Anthem Day: While not specific to Idaho history, March 3 is also National Anthem Day in the United States. This day commemorates the adoption of "The Star-Spangled Banner" as the U.S. national anthem in 1931.