The Oregon Provisional Government was formed with the passing of the Organic Law on July 5, 1843, following the Champoeg meetings that May, where Euro-American emigrants and Hudson's Bay Company employees voted on whether to establish a provisional government for the Oregon country. Euro-American emigrants to Oregon had determined that a governmental structure was necessary to handle issues such as organizing the protection of livestock from predatory animals and settling the estate of Ewing Young, who had died in 1841 without a will.

The Provisional Government consisted of a three-member executive committee, a secretary, a treasurer, and a nine-member legislative committee. In 1845, the three-member executive committee was replaced by a single governor, a role which George Abernethy (1807-1877) filled. The Provisional Government passed laws, instituted taxes, and established a militia in the form of the Oregon Rangers.

In 1848, the United States Congress created the Oregon Territory, and the Provisional Government came to an end in March 1849 with the arrival of Joseph Lane (1801-1881), who had been appointed governor of the Oregon Territory. The Territorial Government lasted until 1859, when Oregon was admitted as the 33rd state of the United States.