My store of knowledge about the 17th president, Andrew Johnson, has until just recently consisted mostly of gaps. He took over after Lincoln’s assassination, was later impeached by the House but saved from conviction by one vote in the Senate, and, uh …

I’m still no expert. But my curiosity has been piqued in ways it never was before and my self-education has commenced.

It started with a goal of visiting the homes of all three Tennesseans to have occupied the presidency: Andrew Jackson, James K. Polk and Johnson. (None of them were actually born in what became the Volunteer State. Polk and Johnson hailed from North Carolina; Jackson – whose birth, like Polk’s, predated Tennessee – entered life in either North or South Carolina. Accounts vary.)

A recent trip to Vol Land made it possible to start with the most distant home, Johnson’s, in Greeneville, a nice little city about an hour or so east of Knoxville.

Just minutes away by foot from our lodgings, a visitor center, two of his homes and his final resting place began my introduction into Johnson’s life and legacy. By all accounts, that legacy is complex. He was, after all, a Jacksonian (yes, that Jackson) Southern Democrat serving as vice president to the Republican Lincoln. Try to imagine that kind of pairing taking place today.

For that matter, try to imagine a president who started his career as a tailor. (His shop is preserved intact in the visitor center.) Apparently, it was a boon occupation for Johnson, who expanded into quite profitable real estate dealings. He soon became noted locally as a political speaker and parlayed his way to office in both houses of the General Assembly, then as governor, then as United States senator.

When Tennessee seceded in 1861, Johnson, an unwavering believer in the Union, became the only senator from a Confederate state not to resign. In 1862, after Union forces took control of Tennessee, Lincoln appointed him military governor of the state.

Then, as his White House presidential biography puts it: “In 1864 the Republicans, contending that their National Union Party was for all loyal men, nominated Johnson, a Southerner and a Democrat, for vice president.”

Fast forward: He and Lincoln were elected, the South surrendered and John Wilkes Booth made a huge mess of what might have been. Johnson, facing that mess, somehow managed to make it messier.

From this point on in history, I need to do a lot more reading and a lot more thinking. It has to do partly with that complex Johnson legacy I mentioned and partly with the lingering resentments between the two sides after the Civil War.

Decades ago, I read the “Profiles in Courage” account of Sen. Edmund G. Ross of Kansas, whose vote against conviction is credited with saving Johnson’s presidency. Political courage is seldom attributed in the service of ignoble causes, so I assumed Johnson’s presidency was somehow worth preserving.

Was it?

A 2018 blog on the National Constitution Center posed this question: “Is Andrew Johnson the Worst President in American History?” It never really answers the provocative question (events of the past decade or so argue no). But it does suggest some of the negative assessments are related to his views on race, which were, to put it mildly, not progressive.

“This is a country for white men, and by God, as long as I am President, it shall be a government for white men,” he wrote in 1866.

Of course he owned slaves, as almost every president before him had. He opposed passage of the Civil Rights Bill and the 14th Amendment, which, among other things, granted citizenship to former slaves. But his impeachment chiefly charged him with violating the Tenure of Office Act by firing Lincoln’s secretary of war, Edwin Stanton, an act that was later repealed and declared unconstitutional, and …

All right. I’m getting way too far into the historical weeds for the purposes of this column. But I’d like to find a readable, engaging biography of Johnson, to help me sort things out. Hey, Jon Meacham, you got any plans?

Next up on my Learn Tennessee Presidential History Tour will be Polk’s home in Columbia. In some ways it should prove to be even more educational than the Johnson outing. At this point my store of Polk knowledge consists entirely of gaps.

Joe Rogers is a former writer for The Tennessean and editor for The New York Times. He is retired and living in Nashville.