1. On June 26, 1876, the Battle of the Little Bighorn took place in southern Montana. Led by Lt. Col. George Armstrong Custer, the 7th Cavalry attacked a group of Lakota Sioux and Northern Cheyenne warriors, resulting in a significant victory for the Native American tribes.

2. June 26, 1892 marks the date that Butte, Montana experienced one of the worst mining disasters in U.S. history. A fire broke out in the Granite Mountain and Speculator Mines, killing 168 miners trapped underground. The tragedy had a significant impact on the town and its mining industry.

3. In 1915, on June 26, the Anaconda Copper Mining Company in Montana was forced to pay a $200,000 settlement for the injuries and deaths caused by a massive explosion at the company's smelter in 1912. The incident, which also led to pollution and health hazards for nearby residents, sparked environmental and safety reforms in the state's mining industry.

4. On June 26, 1929, the Fork Peck Dam was completed in eastern Montana, creating the Fort Peck Reservoir – one of the largest reservoirs in the U.S. Containing over 28 million acre-feet of water, the dam was built by the U.S. Army Corps of Engineers as part of a project to provide irrigation and hydroelectric power to the area.

5. The Montana State Capitol building, located in Helena, was dedicated on June 26, 1902. The neoclassical building, designed by renowned architect Charles Emlen Bell, features a copper dome that is one of the largest in the world. The capitol has since become a symbol of Montana's political and governmental history.