“WE CAN NEVER be satisfied as long as the Negro is the victim of the unspeakable horrors of police brutality.”

More than a half-century ago, the Rev. Martin Luther King Jr. made those words ring out and resonate from the steps of the Lincoln Memorial, a precise century after the Emancipation Proclamation. And when Dr. King delivered his mountaintop sermon of an “I Have a Dream” speech at the 1963 March on Washington, the young man who spoke shortly before him soaked it up, like a salve to his oft-bruised shoulders, which had weathered constant brutality in the South, so often at the hands of Bull Connor’s cops.

In that era, young John Lewis was living to speak of the unspeakable. And today, as a congressman and the lone surviving member of the civil-rights era’s “Big 6,” Rep. Lewis continues to speak and preach, as a voice of steady, nonviolent experience in the face of slayings by police in Ferguson and Brooklyn, in Oakland and Cleveland, as well as American communities that become not symbols, only statistics.

To conclude the new installment in his graphic-novel trilogy of a gripping civil-rights memoir, “March: Book Two” (Top Shelf), Rep. Lewis recounts his impressions of Dr. King’s speech that day. “His words carried through the air like arrows … moving to a climactic refrain the world would never forget,” Lewis writes. “In those moments, Dr. King made plain all of our hopes, our aspirations …. Everything we sought through the beatings and the blood, through the triumphs and the failures. Everything we dared to imagine about a new America, a better America, in which each of God’s children can live in a society that makes love its highest virtue.”

And that, the light of brotherly love, as King is bathed in a white center-spot, is what illuminates how Lewis and his fellow nonviolent protesters ever endured the sheer physical toll depicted with an unblinking eye and brush in “Book Two.”

To understand how our true social heroes are forged, one should sense the heat of their crucible. And through his “March” stories, Lewis — working with two young Southerners, co-author Andrew Aydin and Eisner Award-winning artist Nate Powell — holds our hands close to his high flame.

“Book Two” opens with President Obama’s first inauguration — the type of historic day that Lewis told me he thought he would never see. But then we are soon hurtled back to Nashville, in 1960, to understand how diner sit-ins and movie-theater stand-ins were swirling winds along a gathering national storm.

“Book One,” which fittingly won a special RFK Award (Attorney General Robert F. Kennedy is depicted in this series), could allow for the lightness of Lewis’s youth, as he preached to the family chickens as the son of a poor sharecropper. “Book Two,” by contrast, necessarily cuts quickly to the bloody action. And as police crack protesters’ skulls outside a Tennessee theater showing “The Ten Commandments” — and nearly break “Thou shalt not kill” in the process — the nightsticks’ sick sound echoes with an undeniable resonance in 2015.

Lewis the nonviolent organizer goes on to spend his 21st birthday in jail, and soon is participating in perilous Freedom Rides to the Deep South, to test the Supreme Court’s “Boynton v. Virginia” ruling on desegregated travel.

Even more consistently harrowing than “Book One,” Lewis does not spare us from the onslaught of profanities and pummeling (including the N-word) — these scenes crackle darkly with an inhumanity that could not be conveyed the same by mere prose alone. And when Powell’s chiaroscuro lets us dimly and grimly finally make out what these Freedom Riders see — a sea of whitecaps, as a wave of Klansmen threaten — we feel the sheer fear reflected in the eyes of black and white protesters alike.

The Oscar-nominated film “Selma” may be criticized by some for its depiction of King-LBJ antagonisms, but Lewis delivers firsthand accounts about King and the Kennedys that feel even-handed in rendering the political realities and the conversational skirmishes — as well as JFK’s glowing words to the “Big 6” in the Oval Office, immediately after the ’63 March.

And the bonds between today and yesteryear are especially eloquently illustrated in a double-page “splash” — as Aretha Franklin belts out “Sweet land of liberty!” at the first Obama inauguration, the tiled inset panels stunningly remind of the extreme, excruciating, sometimes fatal sacrifices that made that day in 2009 possible.

And as Dr. King’s words reverberate from his Mall pulpit at book’s end, I am left with one humble dream of my own: That “March,” as a must-read monument for each new generation of students, be stocked in every school and shelved at every library.

As Rep. Lewis continues to carry the civil-rights flame, this graphic achievement is a firsthand beacon that, regrettably, burns ever relevant today.

NOTE: Rep. John Lewis (D-Ga.) and Andrew Aydin will appear tonight at 6:30 at the National Press Club in Washington.