The prosecution of President Andrew Johnson in 1868 was an attempt to restore faith in American’s original ideals.

Ms. Wineapple is the author of “The Impeachers: the Trial of Andrew Johnson and the Dream of a Just Nation.”

When we talk about whether to impeach President Trump, we cite the near impeachment of Richard Nixon or the actual prosecution of Bill Clinton. Oddly, though, we don’t talk much about the first-ever presidential impeachment, which very nearly succeeded in removing Andrew Johnson from office.

In the spring of 1868, his impeachment trial was the hottest thing in town. Walt Whitman often sat in the Senate gallery, and Anthony Trollope finagled a seat when he visited Washington. Men and women lucky enough to receive a color-coded ticket — a different color for each day’s hearing — handed it to uniformed Capitol police officers, who checked them for explosives before they were allowed to enter the building. Reporters pushed into the Senate gallery, furiously scribbling, and newsboys shouted the latest on Washington streets.