He served in the U.S. Senate for twenty-three years, from 1851 to his death, gaining fame as one of the most powerful Radical Republicans, and being notoriously beaten close to death on the Senate floor by a pro-slavery South Carolina congressman.

Early life, education, and law career
Sumner was born in Boston on Irving Street on January 6, 1811. He attended the Boston Latin School. He graduated in 1830 from Harvard College (where he lived in Hollis Hall), and in 1834 from Harvard Law School where he studied jurisprudence with his friend Joseph Story.

In 1834, Sumner was admitted to the bar at the age of twenty-three, and entered private practice in Boston, where he partnered with George Stillman Hillard. A visit to Washington, D.C. filled him with loathing for politics as a career, and he returned to Boston resolved to devote himself to the practice of law. He contributed to the quarterly American Jurist and edited Story's court decisions as well as some law texts. From 1836 to 1837, Sumner lectured at Harvard Law School.

Travels in Europe
From 1837 to 1840, Sumner traveled extensively in Europe. There he learned fluent French, German and Italian, with a command of foreign languages equalled by no American then in public life. He met with many of the leading statesmen in Europe, and secured a deep insight into Continental law and government.

Sumner visited England in 1838 where his knowledge of literature, history, and law made him popular with leaders of thought. Henry Peter Brougham, 1st Baron Brougham and Vaux declared that he "had never met with any man of Sumner's age of such extensive legal knowledge and natural legal intellect." Not until many years after Sumner's death was any other American received so intimately into British intellectual circles.

Beginning of political career
In 1840, at the age of thirty, Sumner returned to Boston to practice law but devoted more time to lecturing at Harvard Law School, to editing court reports, and to contributing to law journals, especially on historical and biographical themes.

A turning point in Sumner's life came when he delivered an Independence Day oration on "The True Grandeur of Nations," in Boston in 1845. He spoke against war, and made an impassioned appeal for freedom and peace.

He was sought after as an orator in the North. His lofty themes and stately eloquence made a profound impression; his platform presence was imposing (he stood six feet and four inches tall, with a massive frame). His voice was clear and of great power; his gestures unconventional and individual, but vigorous and impressive. His literary style was florid, with much detail, allusion, and quotation, often from the Bible as well as ancient Greece and Rome. Henry Wadsworth Longfellow wrote that he delivered speeches "like a cannoneer ramming down cartridges," while Sumner himself said that "you might as well look for a joke in the Book of Revelations."

Sumner cooperated effectively with Horace Mann to improve the system of public education in Massachusetts. He advocated prison reform and opposed the Mexican-American War. He viewed the war as imperialist aggression and was concerned that captured territories would expand slavery westward. In 1847, the vigor with which Sumner denounced a Boston congressman's vote in favor of the declaration of war against Mexico made him a leader of the "conscience Whigs," but he declined to accept their nomination for the House of Representatives.

Sumner took an active part in the organizing of the Free Soil Party, in opposition to the Whigs' nomination of a slave-holding southerner for the presidency. In 1848, he was defeated as a candidate for the U.S. House of Representatives. On December 4, 1849, Sumner argued unsuccessfully before the Massachusetts Supreme Judicial Court in Roberts v. Boston that segregated public schools were unconstitutional.

In 1851, control of the Massachusetts General Court was secured by the Democrats in coalition with the Free Soilers. However, the legislature deadlocked on who should succeed Daniel Webster (who had accepted Millard Fillmore's appointment as Secretary of State) in the U.S. Senate. After filling the state positions with Democrats, the Democrats refused to vote for Sumner (the Free Soilers' choice) and urged the selection of a less radical candidate. An impasse of more than three months ensued, which finally resulted in the election of Sumner by a single vote on April 24.

Service in the Senate

Antebellum career and attack by Preston Brooks (Bully-Brooks Affair)
Sumner took his seat in the Senate on December 1, 1851. For the first few sessions Sumner did not push for any of his controversial causes, but observed the workings of the Senate. On August 26, 1852, Sumner delivered, in spite of strenuous efforts to prevent it, his first major speech. Entitled "Freedom National; Slavery Sectional" (a popular abolitionist motto), Sumner attacked the 1850 Fugitive Slave Act and called for its repeal.

The conventions of both the great parties had just affirmed the finality of every provision of the Compromise of 1850. Reckless of political expediency, Sumner moved that the Fugitive Slave Act be forthwith repealed; and for more than three hours he denounced it as a violation of the Constitution, an affront to the public conscience, and an offense against the divine law. The speech provoked a storm of anger in the South, but the North was heartened to find at last a leader whose courage matched his conscience.

In 1856, during the Bloody Kansas crisis when "border ruffians" approached Lawrence, Kansas, Sumner denounced the Kansas-Nebraska Act in the "Crime against Kansas" speech on May 19 and May 20, two days before the sack of Lawrence. Sumner attacked the authors of the act, Stephen A. Douglas of Illinois and Andrew Butler of South Carolina, comparing Douglas to Don Quixote and Sancho Panza.

The speech contained several mocking references to a speech impediment of Butler ("with incoherent phrases, discharged the loose expectoration of his speech, now upon her representative, and then upon her people") who had suffered a stroke causing the disability. Sumner said Douglas (who was present in the chamber) was a "noise-some, squat, and nameless animal...not a proper model for an American senator," while he said Butler (who was not present) took "a mistress who, though ugly to others, is always lovely to him; though polluted in the sight of the world, is chaste in his sight—I mean, the harlot, Slavery." This slur on Butler's sexual mores would have been considered a deadly insult.

Two days later, on the afternoon of May 22, Preston Brooks, a congressman from South Carolina and Butler's nephew, confronted Sumner as he sat writing at his desk in the almost empty Senate chamber, attaching his postal frank to copies of his speech. Preston said "Mr. Sumner, I have read your speech twice over carefully. It is a libel on South Carolina, and Mr. Butler, who is a relative of mine—" As Sumner began to stand up, Brooks began beating Sumner on the head with a thick gutta-percha cane with a gold head.

Sumner was trapped under the heavy desk (which was bolted to the floor), but Brooks continued to bash Sumner until he ripped the desk from the floor. By this time, Sumner was blinded by his own blood, and he staggered up the aisle and collapsed, lapsing into unconsciousness. Brooks continued to beat Sumner until he broke his cane, then quietly left the chamber.

Sumner was helped to a room outside and was taken home, where he said, "I could not believe that a thing like this was possible." He did not attend the Senate for the next three years, recovering from the attack; Sumner suffered from nightmares, headaches, and post-traumatic shock in addition to the head trauma. The Massachusetts General Court reelected him, in the belief that in the Senate chamber his vacant chair was the most eloquent pleader for free speech and resistance to slavery. Sumner's chair was later purchased by Bates College, an abolitionist leaning school with which Sumner was involved.

The act revealed the increasing polarization of the Union in the years before the American Civil War, as Sumner became a hero in Massachusetts and Brooks a hero in South Carolina. Northerners were outraged, with the editor of the New York Evening Post, William Cullen Bryant, writing:

The South cannot tolerate free speech anywhere, and would stifle it in Washington with the bludgeon and the bowie-knife, as they are now trying to stifle it in Kansas by massacre, rapine, and murder.
Has it come to this, that we must speak with bated breath in the presence of our Southern masters?... Are we to be chastised as they chastise their slaves? Are we too, slaves, slaves for life, a target for their brutal blows, when we do not comport ourselves to please them?"
The outrage heard across the North was loud and strong, and historian William Gienapp later argued that the success of the new Republican party was uncertain in early 1856; but Brooks’s "assault was of critical importance in transforming the struggling Republican party into a major political force."

Conversely, the act was praised by Southern newspapers; the Richmond Enquirer editorialized that Sumner should be caned "every morning," praising the attack as "good in conception, better in execution, and best of all in consequences" and denounced "these vulgar abolitionists in the Senate" who "have been suffered to run too long without collars. They must be lashed into submission."

American Civil War
After years of medically assisted recuperation Sumner returned to the Senate in 1859. He delivered a speech entitled "The Barbarism of Slavery" in the months leading up to the 1860 presidential election. In the critical months following the election of Abraham Lincoln, Sumner was an unyielding foe to every scheme of compromise with the Confederate States of America.

After the withdrawal of the Southern senators, Sumner was made chairman of the U.S. Senate Committee on Foreign Relations in March 1861, a position for which he was well-qualified owing to his years and background of European political knowledge, relationships, and experiences. While the war was in progress, Sumner's letters from Richard Cobden and John Bright, from William Ewart Gladstone and George Douglas Campbell, 8th Duke of Argyll, were read by Sumner at Lincoln's request to the Cabinet, and formed a chief source of knowledge on the political situation in Britain.

In the turmoil over the Trent affair, it was Sumner's word that convinced Lincoln that James M. Mason and John Slidell must be given up. Again and again Sumner used the power incident to his chairmanship to block action which threatened to embroil the U.S. in war with England and France. Sumner openly and boldly advocated the policy of emancipation. Lincoln described Sumner as "my idea of a bishop," and used to consult him as an embodiment of the conscience of the American people.

Sumner was a longtime enemy of United States Chief Justice Roger Taney, and attacked his decision in the Dred Scott v. Sandford case. In 1865, Congress rejected a proposal to commission a bust of Taney to be displayed with the four Chief Justices who preceded him. Sumner said:

I speak what cannot be denied when I declare that the opinion of the Chief Justice in the case of Dred Scott was more thoroughly abominable than anything of the kind in the history of courts. Judicial baseness reached its lowest point on that occasion. You have not forgotten that terrible decision where a most unrighteous judgment was sustained by a falsification of history. Of course, the Constitution of the United States and every principle of Liberty was falsified, but historical truth was falsified also..."

Upon hearing the news of Taney's passing, Sumner wrote Lincoln in celebration declaring that "Providence has given us a victory" in Taney's death.

The Civil War had hardly begun when Sumner put forward his theory of reconstruction, that the South had by its own act become felo de se, committing state suicide via secession, and that they be treated as conquered territories that had never been states. He resented the loose Reconstruction policy taken by Lincoln, and later by Andrew Johnson, as an encroachment upon the powers of Congress.

Throughout the war, Sumner had constituted himself the special champion of blacks, being the most vigorous advocate of emancipation, of enlisting the blacks in the Union army, and of the establishment of the Freedmen's Bureau. A friend of Samuel Gridley Howe, he was also a guiding force for the American Freedmen's Inquiry Commission. Sumner was one of the most prominent advocates for suffrage, along with free homesteads and free public schools for blacks.

Reconstruction years and death
Sumner was strongly opposed to the Reconstruction policy of Johnson, believing it to be far too generous to the South. Johnson was impeached by the House, but the Senate failed to convict him (and thus remove him from office) by a single vote.

Ulysses Grant became a bitter opponent of Sumner in 1870 when the president mistakenly thought that he had secured his support for the annexation of San Domingo.

Sumner had always prized highly his popularity in England, but he unhesitatingly sacrificed it in taking his stand as to the adjustment of claims against England for breaches of neutrality during the war. Sumner laid great stress upon "national claims." He held that England's according the rights of belligerents to the Confederacy had doubled the duration of the war, entailing inestimable loss.

He therefore insisted that England should be required not merely to pay damages for the havoc wreaked by the Confederate Ship Alabama and other cruisers fitted out for Confederate service in her ports, but that, for "that other damage, immense and infinite, caused by the prolongation of the war," the withdrawal of the British flag from this hemisphere could "not be abandoned as a condition or preliminary of such a settlement as is now proposed." (At the Geneva arbitration conference these "national claims" were abandoned.)

Under pressure from the president, on the ground that Sumner was no longer on speaking terms with the Secretary of State, he was deposed in March 1871 from the chairmanship of the Committee on Foreign Relations, in which he had served with great distinction and effectiveness throughout the critical years since 1861. Whether the chief cause of this humiliation was Grant's vindictiveness at Sumner's opposition to his San Domingo project or a genuine fear that the impossible demand, which he insisted should be made upon England, would wreck the prospect of a speedy and honourable adjustment with that country, cannot be determined. In any case it was a cruel blow to a man already broken by racking illness and domestic sorrows. He broke with the Republican party and campaigned for the Liberal Republican in 1872.

Sumner's last years were further saddened by the misconstruction put upon one of his most magnanimous acts. In 1872, he introduced in the Senate a resolution providing that the names of battles with fellow citizens should not be placed on the regimental colors of the United States. The Massachusetts legislature denounced this battle-flag resolution as "an insult to the loyal soldiery of the nation" and as "meeting the unqualified condemnation of the people of the Commonwealth."

For more than a year all efforts– headed by the poet John Greenleaf Whittier– to rescind that censure were without avail, but early in 1874 it was annulled. His last words uttered around his closest collegues and friends was noted to be "save my civil rights bill", a bill which in varied forms would finally pass not until almost 100 years after his death.

He lay in state in the U.S. Capitol rotunda and was buried in Mount Auburn Cemetery.

Sumner was the scholar in politics. He could never be induced to suit his action to the political expediency of the moment. "The slave of principles, I call no party master," was the proud avowal with which he began his service in the Senate. For the tasks of Reconstruction he showed little aptitude. He was less a builder than a prophet.

His was the first clear program proposed in Congress for the reform of the civil service. It was his dauntless courage in denouncing compromise, in demanding the repeal of the Fugitive Slave Act, and in insisting upon emancipation, that made him the chief initiating force in the struggle that put an end to slavery. In St. Louis, Missouri there is a famous high school named after Charles Sumner. The Sumner High school in St. Louis is the first black high school west of the Mississippi.