On September 29, 1863, on a “used” printing press shipped in from Walla Walla, Joseph and Thomas Butler began publishing a weekly newspaper -- the Boise News in Idaho City. The business changed hands the following year and the new owners renamed it the Idaho World. One of their carriers was a youth named James H. Hawley -- who later became a notable lawyer and served as Governor of the state of Idaho.
In 1867, the paper went to a semi-weekly publication schedule, which it continued until 1908, when it returned to a weekly schedule. (For a brief time in 1875, it enjoyed a tri-weekly schedule.) The Idaho World was not the first newspaper published in Idaho; that honor belongs to the Lewiston Golden Age, which began publication in August of 1862. (However, the Age lasted only into 1867.) Thus, the World is the oldest of Idaho’s pioneer newspapers that are still publishing today.
Hiram Taylor French, History of Idaho: A Narrative Account of Its Historical Progress, Its People and Its Principal Interests, Lewis Publishing Co., Chicago and New York (1914).
Newspaper publication information taken from Chronicling America: Historic Newspapers, The Library of Congress (online).