The dome of the U.S. Capitol at sunrise. (Jacquelyn Martin/Associated Press)

Few of them know that the iconic structure and the Capitol Dome are the result of the steadfast efforts of one key senator back in the 1850s.

That was Sen. Jefferson Davis, a Mississippi Democrat and Secretary of War, who left town to head the Confederacy before the building, though well underway, was completed.

Our former colleague Guy Gugliotta, in his splendid new book, “Freedom’s Cap,” gives us a fascinating tale of the struggles to design, fund and construct the new Capitol — at a time when the country was expanding and, at the same time, lurching toward war.

Most of us learned precious little in history class about that period: Bleeding Kansas, Dred Scott, two exceptionally pathetic presidents — Franklin Pierce and James Buchanan — and not a whole lot more.

But Gugliotta deftly weaves a narrative of the difficult and massive construction project and the politics surrounding it. We see how Davis and others foresaw that the still-new nation would become a great power — and deserving of a great building for its seat of government — amid signs that a civil war over slavery was increasingly inevitable.

Indeed, it seems that the notion of constructing the building was about the only thing northern and southern lawmakers could agree on.

Washington observers will be delighted to read that some things never change here. There was constant skirmishing over just about everything, starting with intense bureaucratic infighting between the Army and the Interior Department over control of the effort — the Army won — to disputes over whether to use federal workers or to contract out.

The lawmakers bickered over the scope and design of the project and the yearly funding for it. Lobbyists fought over lucrative contracts while losers pushed for bogus investigations.

There were selective media leaks to undermine political enemies as well as outraged protests from the Know-Nothing Party — a nativist, anti-Catholic group — that Italian and Irish immigrant workers were taking jobs away from Americans.

Some things, of course, were slightly different. By December 1859, a large number of lawmakers were armed, Gugliotta writes, and a “near-riot began” when a pistol accidentally fell out of one lawmaker’s pocket.

“The only persons who do not have a revolver and a knife,” one senator wrote, “are those who have two revolvers.”

Gugliotta dryly observes: “The age of accommodation was over.”

Great reading for spring break.