Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Territory of Idaho was an organized incorporated territory of the United States that existed from March 4, 1863, until July 3, 1890, when the final extent of the territory was admitted to the Union as the State of Idaho. The territory was officially organized on March 4, 1863 by Act of Congress, and signed into law by President Abraham Lincoln.