Castle Hill is a rock outcrop about 60 feet high. Families of the Kiksadi clan of Tlingit lived here before the Russians came, and the Tlingit name for the hill is Noow Tlein. In 1804 Alexander Baranov of the Russian-American Company took the hill after the six-day Battle of Sitka.
From 1806 it was the seat of government for Russian Alaska. The last building on top, a brick Governor's House with a cupola, was built in 1836 and burned in 1894.
The transfer of Alaska to the United States took place here in a ceremony on October 18, 1867. In 1959 the first 49-star flag in Alaska was raised here, in an unofficial and secret ceremony. It became a National Historic Landmark in 1962.