The Department of Alaska was the designation for the government of Alaska from its purchase by the United States of America in 1867 until its organization as the District of Alaska in 1884. During the department era, Alaska was variously under the jurisdiction of the U.S. Army (until 1877), the U.S. Dept. of the Treasury (from 1877 until 1879) and the U.S. Navy (from 1879 until 1884). The area later became the District of Alaska, then the Territory of Alaska, then the State of Alaska.
At the instigation of U.S. Secretary of State William Seward, the United States Senate approved the purchase of Alaska from Russia for $7,200,000 on April 9, 1867, and the United States flag was raised on October 18 of that same year (now called Alaska Day). Coincident with the ownership change, the de facto International Date Line was moved westward, and Alaska changed from the Julian calendar to the Gregorian calendar. Therefore, for residents, Friday, October 6, 1867 was followed by Friday, October 18, 1867; two Fridays in a row because of the date line shift.
On the morning of October 18, 1867, USS Ossipee arrived at Sitka with Russian Commissioner Captain Alexis Pestchouroff and American Commissioner General Lovell Rousseau on board. That afternoon, 250 American soldiers, 80 Russian soldiers, Russian-American Company Chief Manager Prince Maksutov and his wife, and a group of locals assembled at the flagstaff in front of the governor's residence (on what has come to be known as "Baranof (Baronov) Castle Hill" to witness the flag of Russia being lowered and the U.S. flag being raised in its place.