1. On April 20, 1877, the Nez Perce War began in Montana. The conflict, which lasted four months, saw a series of battles between the United States Army and a group of Native American tribes led by Chief Joseph.

2. In 1909, the Montana State Capitol building was completed in Helena. Designed by architect Frank Mills Andrews, the Capitol features a copper dome that is one of Montana's most recognizable landmarks.

3. On April 20, 1910, the worst avalanche in United States history occurred in the Cascade Mountains of Washington. Known as the Wellington disaster, the avalanche killed 96 people, including many passengers on the Great Northern Railway.

4. In 1967, the Montana State Senate approved an act that made Montana the first state in the nation to specifically allow the use of marijuana for medical purposes. The law, which was later amended, laid the groundwork for the legalization of medical marijuana in other states.

5. April 20, 1993, saw the opening of the Lewis and Clark Interpretive Center in Great Falls. The museum showcases the history of the Lewis and Clark Expedition and its impact on Montana and the surrounding region.