1. On June 12, 1920, the U.S. Forest Service established the Bob Marshall Wilderness in Montana. This wilderness area covers over 1 million acres of pristine Rocky Mountain wilderness and is named after conservationist Bob Marshall who advocated for the preservation of natural areas.

2. On June 12, 1929, the oil boomtown of Roundup, Montana experienced a devastating tornado. The tornado destroyed over 40 homes and buildings and killed eight people. This event is one of the most destructive tornadoes in Montana history.

3. June 12, 1937, marked the opening of the Fort Peck Dam in northeastern Montana. The dam, which is one of the largest earth-filled dams in the world, was built by the U.S. Army Corps of Engineers to provide hydroelectric power and flood control for the Missouri River Basin.

4. In 1966, Montana State University in Bozeman received a donation of $25 million from the Gianforte Family Foundation. This was the largest donation ever made to a public university in the state of Montana, and it helped fund the construction of several new buildings on the MSU campus.

5. On June 12, 2009, Montana experienced a record-breaking heatwave with temperatures hitting over 100 degrees Fahrenheit in some parts of the state. This heatwave contributed to several wildfires in the state, including the devastating Rock Creek fire which burned over 2,500 acres of land near Red Lodge.