Its tall central rotunda and upper dome and tower roofs are covered in zinc metal alloy to provide a silvery facade which does not weather or corrode.

It was primarily focused on the west wing, to upgrade its life safety, complying with the earlier Americans with Disabilities Act of 1990 for modern handicapped persons accessibility and reworking utility mechanical, electrical and plumbing infrastructure of the century and a quarter old building as well as architectural improvements to bring the capitol closer to its original 1870s / 1880s appearance, the "period of significance" for the monumental building.

Improvements included cleaning and refinishing of interior walls and ceilings, along with exposed brick arches in the basement; installation of maiden lamp posts for the grand staircase, new chandeliers, and copper-clad exterior doors; and removal of a second floor mezzanine level.

Piquenard was also coincidentally architect for the neighboring Iowa State Capitol being built in Des Moines, which is of a similar architectural style, albeit only 3/4 of the larger size building in Springfield.

[8] The scheduled work will also remove now undesirable asbestos substances first installed decades before, and add an additional underground parking garage (to remove outside campus unsightly car parking lots returning the surrounding landscaped grounds to people, and along with a citizens visitor screening area to improve Capitol security in light of recent news events of prior decades.

Current project work will remove these as was also earlier done a decade before in the west wing and to clean / restore the original walls of their decorative interior paint scheme colors.

Kaskaskia had been an administrative center and on the main inland transportation route for much of the 18th century between the Great Lakes and south to the French and then Spanish colonial port city of New Orleans at the mouth of the Mississippi near the Gulf of Mexico.

It became the largest town in the western Illinois Country, ceded by the Kingdom of Great Britain in 1783 after the American Revolutionary War to the newly independent United States.

Wishing to site the capital in the state's interior from its border on the Mississippi, the first General Assembly of Illinois petitioned the U.S. Congress in Washington for a grant of suitable federal public land.

The new state of Illinois allowed its lease on the first capital in the river port town of Kaskaskia to expire and relocated its government and courts upstream northeast to Vandalia.

[11] After 16 years of work, in 1853, the fifth Illinois Capitol was completed and the first in Springfield for a total sum of $260,000 (equivalent to $9,522,240 in 2023), almost twenty times the cost of any such previous structure.

The fifth capitol is closely associated with local New Salem storekeeper, splitter of logs and rails, later to become the self-educated, voracious reader becoming a Springfield lawyer and future 16th President Abraham Lincoln (1809-1865, served 1861-1865), It was here that he argued cases before the local magistrates as a circuit rider elevating to the courthouse of the Illinois Supreme Court, served in the Illinois General Assembly (state legislature), first debated Senator Stephen Douglas, for elections in 1858 to be chosen United States Senator from Illinois to Washington, delivered his famous "House Divided" speech in June 1858, his farewell remarks in February 1861, at the local railroad station before leaving on his cross-country train journey to the White House, and returned four years later in a black-draped funeral mourning car to lay in state in death after his assassination at Ford's Theatre on April 14, 1865, later to be interred in the Lincoln Tomb.

As Illinois prospered and experienced several booms in population, economic and industrial growth, the fifth Capitol became crowded, especially as a result of relocations after the American Civil War (1861-1865).