1. Montana became a state on November 8, 1889, but March 21 marks the anniversary of when President Abraham Lincoln signed the Homestead Act of 1864 that opened up the land to settlement. This act granted land to individuals who agreed to settle on and improve the land for at least five years.

2. On March 21, 1872, Yellowstone National Park was established by an Act of Congress. It was the world's first national park, covering over 2.2 million acres in Montana, Wyoming, and Idaho.

3. The deadliest avalanche in Montana history occurred on March 21, 1910, at the Great Northern Railway's division point of Wellington. The avalanche claimed the lives of 96 people, including passengers and crew members aboard two trains.

4. In 1933, the U.S. Congress passed the Custer Battlefield National Monument Act, which established a national monument to preserve and interpret the history of the 1876 Battle of the Little Bighorn. The monument is located in Big Horn County, Montana.

5. On March 21, 1983, the Anaconda Company's copper smelter in Anaconda, Montana, was shut down. The smelter had been a major employer in the area, but concerns over pollution and declining copper prices led to the closure. The landmark 585-foot-tall brick stack remained standing until it was finally demolished in 2019.