FREEDOM’S CAP: The United States Capitol and the Coming of the Civil War. By Guy Gugliotta. Hill and Wang. 512 pages. $35.

In 1851, construction workers began transforming the U.S. Capitol into the awe-inspiring landmark that it is today.

It was a bold, expansive project. The Capitol featured substantially longer wings and a giant cast-iron dome, executed in the neoclassical style and faced with majestic white marble. Construction finished 12 years later when workers topped it with the statue “Freedom Triumphant in War and Peace.”

Guy Gugliotta frames his book around a difference of opinion regarding an earlier version of the statue. Freedom originally wore a “liberty cap,” the symbol of a liberated slave. While the engineer Capt. Montgomery Meigs saw no problem with it, Secretary of War Jefferson Davis took objection on the grounds that Americans “were always free ... not slaves just released.”

Davis won in the end. The final version of “Freedom” wore no liberty cap.

Gugliotta draws attention to the disagreement throughout the book, but, regrettably, he does not make it clear how this disagreement mirrored larger national conflicts over slavery.

That criticism notwithstanding, Gugliotta has researched and written a skillful narrative that brings the U.S. Capitol to life. “Freedom’s Cap” is at its finest when delving deep into the messy politics and personal rivalries behind this massive government project. Readers will be captivated by the central paradox of this book: a grand Capitol being built at the same time that the country slipped into bloody civil war.

Reviewer Nathan P. Johnson, acting curator at Fort Sumter National Monument