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The state of Montana was once home to a massive inland sea that covered much of North America around 80 million years ago during the Late Cretaceous period.
Petroleum County, Montana, located in the central part of the state, has a unique history tied to its rich oil and natural resources. The area, originally inhabited by Native American tribes such as the Crow and Sioux, experienced increased exploration and settlement in the late 19th century when oil was discovered.

In the late 1800s, prospectors and drillers flocked to Petroleum County in search of oil and natural gas. The first significant oil well was drilled in 1902, and it marked the beginning of an oil boom in the region. The discovery of the Cat Creek Oil Field in 1908 further fueled the development and growth of the county. As oil extraction intensified, numerous oil wells and refineries were established, attracting both investors and workers to the area.

During the early 20th century, Petroleum County witnessed rapid economic growth and population expansion. New towns and settlements sprung up, catering to the needs of the booming oil industry. The county became home to the largest oil refinery in the state, providing a significant source of employment for local residents. However, the boom was short-lived, as the Great Depression and the decline in oil prices in the 1930s led to a significant downturn in the industry. Many oil wells were abandoned, and the population declined as people moved elsewhere in search of new opportunities.

Since the decline of the oil industry, Petroleum County has shifted its focus towards agriculture and tourism. The vast landscapes and pristine natural beauty of the area attract outdoor enthusiasts who enjoy hunting, fishing, and camping. The county is also known for its important role in Montana's ranching industry, with numerous cattle and sheep ranches dotting the countryside.

Overall, the history of Petroleum County is one of discovery, boom, and subsequent decline in the oil industry. Today, the county thrives on its agricultural and recreational opportunities, while still maintaining ties to its rich petroleum heritage.

This timeline provides a concise overview of the key events in the history of Petroleum County, Montana.

  • 1914 - Petroleum County is established on February 25.
  • 1930s - The Great Depression hinders development in the county.
  • 1951 - The first oil discovery is made in the Cat Creek area.
  • 1954 - The town of Winnett becomes the county seat.
  • 1978 - Oil production reaches its peak in the county.
  • 1980s - Oil prices decline, leading to decreased drilling activity.
  • 1992 - The Cat Creek Oil Field is permanently abandoned.
  • Early 2000s - The county's economy diversifies with tourism and renewable energy developments.
  • 2010 - Petroleum County celebrates its 100th anniversary.
  • 2018 - The population of Petroleum County is estimated to be around 460 people.