It continued as such following the admission of the Territory as the 43rd state in the federal Union on July 3, 1890, the day before Independence Day, the Fourth of July, when a 43rd white star was added officially to the constellation in the upper corner blue field (canton) of the red and white striped American Flag ("Old Glory" / "the Stars and Stripes").

[3] Its sandstone exterior is dug and cut from the state-owned quarry at nearby Table Rock in Ada County, Idaho.

Architectural inspirations included St. Peter’s Basilica in Rome, St Paul's Cathedral in London and the U.S. Capitol in Washington, D.C.

On the north side of the second floor rotunda is a sculpture of George Washington astride a horse; to its rear is the attorney general’s suite of offices, which formerly housed the Idaho Supreme Court, until its current building opened in 1970.

Balcony entrances on the fourth floor of the senate and house galleries, which enable the public to observe the legislature in session.

In 2000, the evaluation master plan was completed and its total cost estimate put at $64 million dollars to do a proper job of lasting quality.

In 2001, the Legislature granted a one-time appropriation of $32 million dollars; and bonds were issued to cover the other half of the Capitol project.

In 2002–2003, crews completed Phase II of the project, which involved exterior facade repairs financed with a supplementary $1.5 million dollars appropriation for that purpose.

In 2005, an increase in the state cigarette / tobacco tax helped pay for additional interior restoration expenses totaling $20 million dollars.

After legislators agreed to this budget modification, construction began and continued until 2010, when both interior and exterior renovations were finished.

Plasterers were tasked with restoring scagliola, a composite of selenite, glue, and natural pigments, imitating marble and other hard stones.

[5] In 1958, Shadduck was elected the state's Secretary of Commerce and Development – the first woman to hold that office in the Governor's executive cabinet.

A full-scale replica of the Liberty Bell (uncracked) occupies a site at the base of the stairs outside the Jefferson Street entrance.