Complex sentence: The Territory of Alaska was an incorporated territory of the United States from August 24,1912 to January 3,1959, when it was admitted to the Union as the State of Alaska.
Split into simpler sentences: The Territory of Alaska was an incorporated territory of the United States from August 24,1912, to January 3,1959. On the latter date, the Territory of Alaska was admitted to the Union as the State of Alaska.