1. In 1861, Colorado Territory was established by the United States Congress, making it a federal territory. This was a significant event in Colorado history as it marked the beginning of an era of formal government and law.

2. May 13, 1934 was a day of extreme weather in Colorado, with record-breaking high temperatures in some areas and heavy snowfall in others. This unusual weather event was caused by a combination of a low-pressure system and high-altitude winds.

3. On May 13, 1942, a train carrying U.S. Army troops derailed near Pueblo, Colorado, killing 29 soldiers and injuring many more. The accident was caused by a broken rail on the tracks and is still considered one of the deadliest train accidents in Colorado history.

4. In 1958, the first major ski resort in Colorado, Vail, opened to the public. The resort was founded by Pete Seibert and Earl Eaton and quickly became one of the most popular ski destinations in the United States.

5. On May 13, 1975, the first oil shale mining lease in the United States was awarded by the federal government to the Exxon Corporation. This marked a major turning point in the history of the energy industry in Colorado, as oil shale became an important resource for the state in the decades that followed. However, the industry eventually declined due to environmental concerns and economic factors.