sentences:  The Treaty of Saint Petersburg of 1825 defined the boundaries between Russian America and British Empire claims and possessions in the Pacific Northwest.The United States purchased Alaska from the Russian Empire on March 30, 1867.Originally organized as the Department of Alaska (1867–1884), the area was renamed as the District of Alaska (1884–1912) and the Territory of Alaska (1912–1959) before it was admitted to the Union as the State of Alaska (1959–present).