1. 1864: The Battle of Canyon Ferry - On August 23, 1864, the Battle of Canyon Ferry took place in what is now Lewis and Clark County, Montana. This battle was part of the larger conflict between the United States and various Native American tribes, often referred to as the Indian Wars. Members of the U.S. Army's 2nd Colorado Cavalry engaged with a group of Cheyenne and Arapaho warriors, resulting in a victory for the U.S. forces.

2. 1891: Montana becomes a state - On August 23, 1891, Montana officially became the 41st state in the United States. Montana was originally part of several different territories, including the Oregon Territory, the Washington Territory, and the Dakota Territory, before becoming its own territory in 1864. It took several attempts and several years of lobbying before Montana was finally granted statehood.

3. 1934: The Wilderness Act - On August 23, 1934, a bill was introduced in the U.S. Congress that would eventually become the Wilderness Act of 1964. This landmark legislation established a system for preserving wilderness areas in the United States, and has had a profound impact on the way we think about and manage our natural resources.

4. 1960: The Montana State Capitol building is completed - On August 23, 1960, the Montana State Capitol building in Helena was finally completed after more than 50 years of planning and construction. The Capitol building is a neoclassical structure that features a grand dome, columns, and other elegant architectural details. It is now one of the most recognizable landmarks in the state of Montana.

5. 1995: The Unabomber is arrested - On August 23, 1995, Ted Kaczynski, also known as the Unabomber, was arrested in a cabin near Lincoln, Montana. Kaczynski had been sending letter bombs to various targets for nearly two decades, killing three people and injuring many others. His arrest was a major breakthrough in the case, and he eventually pleaded guilty and was sentenced to life in prison without the possibility of parole.