1. On April 21, 1938, the city of Bonners Ferry experienced the worst flood in its history. The Kootenai River overflowed its banks, causing significant damage to homes and businesses in the area.

2. In 1904, on April 21st, a group of miners in the Coeur d'Alene mining district in northern Idaho went on strike, demanding better wages and working conditions. The strike ultimately led to the creation of the Western Federation of Miners.

3. On April 21, 1865, Idaho's Territorial Legislature convened for the first time in Lewiston. This marked the beginning of Idaho's formal governance and the establishment of the territorial capital.

4. The Idaho State Capitol building in Boise was officially dedicated on April 21, 1920. The Capitol is one of the largest and most ornate state capitols in the country, featuring unique architectural features like the rotunda and the eagle motif.

5. On April 21, 1976, the Idaho State Board of Education voted to officially change the name of Boise State College to Boise State University. This change reflected the growth and expansion of the institution, which had become one of Idaho's largest universities.