1. The Battle of the Rosebud: On June 23, 1876, the Battle of the Rosebud took place in Montana between US troops led by General Crook and Native American forces led by Crazy Horse. It was a significant prelude to the infamous Battle of Little Bighorn.

2. Montana's Statehood: Montana officially became the 41st state of the Union on June 23, 1889, after years of territorial status.

3. Montana's First Radio Station: On June 23, 1922, KGHL - Montana's first radio station - began broadcasting from Billings. It was initially used to entertain farmers and ranchers with music and market reports.

4. Opening of the Going-to-the-Sun Road: On June 23, 1933, the Going-to-the-Sun Road - a scenic highway through Glacier National Park - was opened to the public. The construction of the road took almost 20 years and is considered a remarkable feat of engineering.

5. Montana's Nuclear Holocaust Survival Plan: The Montana State Legislature approved a controversial nuclear war survival plan on June 23, 1983. The plan called for the construction of fallout shelters and the stockpiling of supplies in case of a nuclear attack. It was met with criticism and scorn from many who saw it as pointless and impractical.