His father, John Ingersoll, was an abolitionist preacher. Ingersoll was born in Dresden, New York, but his family moved frequently because of his father's radical views before finally settling in Peoria, Illinois. Ingersoll apprenticed himself to lawyers there and hung out his shingle.

With the advent of the American Civil War, he raised the 11th Illinois Cavalry Regiment and took command. The regiment fought in the Battle of Shiloh. Ingersoll was later captured, then paroled on his promise that he would not fight again. (This was common practice early in the war.)

After the war, he served as Illinois Attorney General. He was a prominent member of the Republican Party. Although he never held any office, he was an active participant. His nominating speech for James G. Blaine in 1876 did not result in Blaine's candidacy, but the speech itself, known as the "Plumed Knight" speech, was considered the gold standard for political oratory.

Ingersoll was involved in several prominent trials as an attorney, notably the Star Route trials, a major political scandal in which his clients were acquitted. He also defended a New Jersey man for blasphemy. Although he did not win acquittal, his vigorous defense is considered to have discredited blasphemy laws and few other prosecutions followed.

Ingersoll was most noted as an orator, the most popular of the age, when oratory was public entertainment. He spoke on every subject, from Shakespeare to Reconstruction, but his most popular subjects were atheism and the sanctity and refuge of the family. He committed his speeches to memory although they were sometimes more than three hours long. His audiences were said never to be restless.

His radical views on religion, slavery, woman's suffrage, and other issues of the day effectively prevented him from ever pursuing or holding political offices higher than that of Attorney General. Illinois Republicans tried to pressure him into running for Governor on the condition that Ingersoll conceal his atheism during the campaign. He refused the nomination because he thought concealing information from the public was immoral.

Many of Ingersoll's speeches advocated freethought and humanism, and often poked fun at religious belief. For this the press often attacked him, but neither his views nor the negative press could stop his rising popularity. At the height of Ingersoll's fame, audiences would pay $1 or more to hear him speak, a giant sum for his day.

Ingersoll died of heart failure at age 65. Soon after his death, Clinton P. Farrell, a brother-in-law, collected copies of Ingersoll’s speeches for publication. The 12-volume Dresden Editions kept interest in Ingersoll's ideas alive and preserved his speeches for future generations.

Quotations

"There are no Gods, no angels, no devils, no heaven or hell. There is only our natural world. Religion is but myth and superstition that hardens the hearts and enslaves minds."

"A crime against god is a demonstrated impossibility."

"A good deed is the best prayer."

"Age after age, the strong have trampled upon the weak; the crafty and heartless have ensnared and enslaved the simple and innocent, and nowhere, in all the annals of mankind, has any god succored the oppressed."

"Blasphemy is an epithet bestowed by superstition upon common sense."

"Courage without conscience is a wild beast."

"Each nation has created a god, and the god has always resembled his creators. He hated and loved what they hated and loved, and he invariably found on the side of those in power. Each god was intensely patriotic, and detested all nations but his own."

"Every library is an arsenal."

"For the most part, colleges are places where pebbles are polished and diamonds are dimmed."

"The hands that help are far better than the lips that pray."

"The man who invented the telescope found out more about heaven than the closed eyes of prayer ever discovered."

"In nature there are neither rewards nor punishments - there are consequences."

"I admit that reason is a small and feeble flame, a flickering torch by stumblers carried in the star-less night, blown and flared by passion's storm, and yet, it is the only light. Extinguish that, and nought remains."

"Good-by, gentlemen! I am not asking to be Governor of Illinois ... I have in my composition that which I have declared to the world as my views upon religion. My position I would not, under any circumstances, not even for my life, seem to renounce. I would rather refuse to be President of the United States than to do so. My religious belief is my own. It belongs to me, not to the State of Illinois. I would not smother one sentiment of my heart to be the Emperor of the round world."

"Churches are becoming political organizations.... It probably will not be long until the churches will divide as sharply upon political, as upon theological questions; and when that day comes, if there are not liberals enough to hold the balance of power, this Government will be destroyed. The liberty of man is not safe in the hands of any church. Wherever the Bible and sword are in partnership, man is a slave. All laws for the purpose of making man worship God, are born of the same spirit that kindled the fires of the auto da fe, and lovingly built the dungeons of the Inquisition. All laws defining and punishing blasphemy -- making it a crime to give your honest ideas about the Bible, or to laugh at the ignorance of the ancient Jews, or to enjoy yourself on the Sabbath, or to give your opinion of Jehovah, were passed by impudent bigots, and should be at once repealed by honest men. An infinite God ought to be able to protect himself, without going in partnership with State Legislatures. Certainly he ought not so to act that laws become necessary to keep him from being laughed at. No one thinks of protecting Shakespeare from ridicule, by the threat of fine and imprisonment. It strikes me that God might write a book that would not necessarily excite the laughter of his children. In fact, I think it would be safe to say that a real God could produce a work that would excite the admiration of mankind. Surely politicians could be better employed than in passing laws to protect the literary reputation of the Jewish God."

"One good schoolteacher is worth more than 100 priests."