We have some giant TV’s in our newsroom that are tuned into the major cable news networks, silently blasting the latest headlines and prescription drug ads into my peripheral vision, all day long.

But around 5 o’clock on Tuesday something weird happened. Somebody turned on the sound.

So, for about 10 minutes, along with a handful of colleagues, I stood by my desk and watched Nancy Pelosi, the speaker of the U.S. House of Representatives, announce the beginning of a formal impeachment inquiry into the president of the United States. The Congress will investigate, she said, whether President Trump corruptly abused the power of his office  to manipulate a foreign government into interfering in the next U.S. election on his behalf.

The announcement wasn’t shocking news — reports had been coming out all day that this was what she intended to do. But it was history.

There have only been three presidential impeachments. Most middle-age Americans remember when Bill Clinton was tried in the Senate for lying under oath about his sexual relationship with a White House intern. 

Older folks remember Richard Nixon’s resignation, which came before he was formally impeached by the House but shortly after a group of Republican senators told him that he would not survive a vote to remove him from office.

But the impeachment case that no one is old enough to remember maybe the most relevant to our time, and that was the attempt to remove President Andrew Johnson from office in 1868. It wasn’t just a trial of one politician’s wrongdoing but also a question of national identity and character.

I always lumped it in with the “boring part” of U.S. History — between the Lincoln assassination and arrival of Teddy Roosevelt. But this summer I read “The Impeachers” by Barbara Wineapple and realized that the failure to impeach Johnson was a historical turning point, one that set back the dream of a just nation for at least century.

It’s relevant today for a number of reasons. Like Trump, Johnson did not come to the presidency by the usual path. He was Lincoln’s second vice president, put on the 1864 ticket despite the fact that he was a Democrat and a Southerner. Johnson had been loyal to the union during the Civil War, and that made him look like a good person to have on the team when it came time to reconstruct the nation.

But when Lincoln was murdered, some other facts about Johnson became more problematic. For starters, he had been a slave owner and remained a white supremacist, sympathetic with the Old South except on the issue of secession.

He did not believe that freedmen and women were worthy of citizenship or the right to vote. He wanted to pardon Confederates and welcome the rebel states back into the Union as if they had never left. 

Even when there were massacres of blacks in New Orleans and Memphis, and the rise of the original Ku Klux Klan terrorizing former slaves, Johnson opposed sending U.S. troops to the South, saying it was a local police matter.

As with Trump, there were people ready to impeach Johnson from his first day in office. Abolitionists like Rep. Thaddeus Stevens of Pennsylvania wanted much more than the end of slavery. They wanted to build a free, multiracial democracy where everyone was truly equal. That’s what the war had been about, and that’s what Johnson was undoing.

Stevens and the others pressured their colleagues to impeach Johnson. The impeachers started out as a minority but gained ground as the president defied Congress and refused to submit to the constitutional limits on his power. The last straw came when he fired the Secretary of War Edwin Stanton after being expressly forbidden from doing so by law.

Johnson survived his trial in the Senate, probably because Sen. Edmund Ross of Kansas, one of John F. Kennedy’s “Profiles in Courage,” had been bribed. But Wineapple concludes that the impeachment was not a failure.

“It demonstrated that the American President is not a king, that all actions have consequences and that the national government , conceived in hope, with its checks and balances, could maintain itself without war… (Impeachment) had not succeeded, but it had worked.”

Trump’s impeachment is not history yet. It’s still news, and there’s no way of knowing what’s going to happen.

But standing in the newsroom last week, listening to Pelosi’s speech, I couldn’t escape the feeling that we’ve stepped into another one of those turning points where we will find out what kind of country we are and what we want to become.

The echoes of what will be said and done over the next few months will be with us for a long, long time.

Greg Kesich is editorial page editor for the Portland Press Herald.