Location: Winnett, Petroleum County
On February 28, 1925, Petroleum County was officially created, becoming the 56th and last county established in Montana. Carved out of a portion of Fergus County, its formation marked the culmination of a period of extensive county reorganization and creation in the state, driven by settlement patterns and the development of local economies. The county was named for the oil discoveries that had begun to shape its economic landscape, reflecting the growing importance of the petroleum industry in Montana. Winnett was designated as the county seat, serving as the administrative and commercial center for this sparsely populated but resource-rich region. The creation of Petroleum County underscored the state's ongoing efforts to provide localized governance and services to its diverse communities, even in its most remote areas. This event represents the final chapter in the geographical and administrative partitioning of Montana into its current county structure, solidifying the state's internal political boundaries. The establishment of Petroleum County on this day is a historical marker of Montana's development, showcasing its adaptability to economic changes and its commitment to local representation across its vast territory.