After Dr. McLoughlin sent his resignation to the Hudson's Bay Company, in 1845, he determined to become a citizen of the United States. In 1845 he consulted with Peter H. Burnett, then Chief-Justice of the Provisional Government, and with Jesse Applegate, about taking the oath of allegiance to the United States, and taking out his first naturalization papers, but Burnett had no authority from the United States, or other jurisdiction, to administer such an oath (or to issue such papers) and so advised Dr. McLoughlin. Although this matter was well known in Oregon, it gave Dr. McLoughlin's enemies a chance to say that he was a British subject, and had not taken the oath of allegiance to the United States, nor applied to become a citizen of the United States. August 14, 1848, the bill establishing the Territory of Oregon became a law. March 2, 1849, General Joseph Lane, the first Territorial Governor of Oregon, arrived at Oregon City. March 3, 1849, he issued his proclamation assuming charge as governor. Soon after the Territory of Oregon was organized and courts of the United States established. The assignment of Judges to their respective districts was made May 13, 1849. May 30, 1849, Dr. McLoughlin took the oath and made his declaration to become a citizen of the United States, as required by the naturalization law. So he acted with promptness. This was well known in Oregon at the time. Dr. McLoughlin voted at Oregon City at the first general election held in June, 1849, but he did not vote for Thurston as delegate to Congress, which Thurston knew. Under the act of Congress, organizing Oregon as a territory, all aliens who had declared, on oath, their intentions to become citizens of the United States, and taken an oath to support the Constitution of the United States and the provisions of the act establishing the Territorial Government of Oregon, were entitled to vote at the first election. Dr. McLoughlin became a citizen of the United States, at Oregon City, September 5, 1851. The naturalization law then allowed an alien to become a citizen of the United States two years after taking the oath and making his declaration, if he had lived in the United States for five years. His witnesses were A. L. Lovejoy, A. A. Skinner, and Theodore Magruder. His admission to citizenship was based on his said oath and declaration of May 30, 1849.