Bret Harte (1836-1902)	Short-story writer and editor. Bret Harte rose to prominence as a San Francisco writer during the 1860s and 70s. After Sam Clemens came to California in 1865, Bret helped him get published in several publications. While writing The Innocents Abroad in San Francisco in 1868, Bret provided editorial assistance in exchange for being allowed to publish excerpts in the Overland Monthly, of which he was editor. In 1876, Bret came to the Clemenses house in Hartford, Connecticut, where he wrote one of his major stories, Thankful Blossom. Bret and Sam also collaborated on the play Ah Sin. While working on the play and in the immediate aftermath, Bret and Sam became embroiled in a bickering argument, which would lead to their falling out. For the remainder of his life, Sam would have an very negative opinion of Harte as a person, while always respecting his ability as a writer.
William Dean Howells (1837-1920)	Very respected and influential editor, writer, and critic from the late 1860s on. W.D. Howells began his career in literature as an editor for the Nation magazine after the Civil War. By 1867, he became an assistant editor for the Atlantic Monthly, the most important literary magazines in the country. After a positive review for The Innocents Abroad in 1869, Sam Clemens went to thank Howells in person at his Boston office. The ensuing friendship between the two lasted for the rest of their lives. Howells had a important role in the progression of Mark Twain's career as an author. Clemens would have Howells read his manuscripts and listen to his ideas regarding new works. Howells would give advice on which writings should be published, as well as reviewing his books in the Atlantic. As well, Howells published Twain's work in his magazine. After Clemens' death, Howells wrote My Mark Twain, an account of their lifelong friendship. In the book, Howells calls Twain the "Lincoln of our literature." Following his tenure as Atlantic editor, Howells wrote several novels, and contributed to Harper's Magazine. At the end of his life, he became the first president of the American Academy of Arts and Letters.
Paige Compositor	Automatic typesetting machine. Invented by James Paige from the 1870s to 1894, the Compositor was heavily financied by Sam Clemens, which led to his financial ruin. The Compositor was intended to print pages significantly faster than by using manual typesetting; the newspaper industry was the intended market. However, the advent of the linotype machine proved to be more reliable and practicle, if not as fast. Following an unsuccessful test run at the Chicago Herald in 1894, the machine was deemed a failure. The monetary loss suffered by Clemens led to the demise of his publishing company, Charles L. Webster.
Albert Bigelow Paine (1861-1937)	Sam Clemens' biographer, literary executor, and the first editor of the Mark Twain Papers. Albert Paine, a successful novelist and short story writer first met Sam Clemens at a club dinner in New York City in 1901. They began a correspondence, which led to Paine approaching Clemens about be his biographer. Clemens enthusiastically agreed to the proposal. By January 1906, Paine was living in the Clemens home, and was Sam's companion for the remainder of his life. Paine conducted extensive research about the life of Clemens, sifting through unpublished manuscripts and visiting places where Clemens spent periods of his life. After Clemens' death in 1910, Paine was named literary executor, and had complete control over all of Twain's unpublished writings. Working closely with Clara Clemens, Paine fashioned a public persona of Twain that showed the utmost respect to the deceased writer. In 1912, Paine published Mark Twain, A Biography, a massive three-volume work considered the most ambitious biography of Twain ever written. Paine would freely edit the unpublished manuscripts, striking out sections to maintain the image of Twain that he believed the world should see; unfortunately, he made no indication exactly which sections had been tampered with. It would take decades for scholars to determine the influence of his editing on the manuscripts. Under Paine's influence, a dozen books of unpublished writings were released, including: The Mysterious Stranger, which was completely reworked by Paine and Harper' editor Frederick Duneka, yet presented as a novel solely written by Twain; Mark Twain's Autobiography, using only 30% of the autobiographical writings in existance; a collection of 450 letters; and a selection from Twain's notebooks.
Joseph Twitchell (1838-1918)	Hartford-based Congregationalist clergyman; one of Sam Clemens' closest friends. Joseph Twitchell led a Congregationalist church in Hartford's affluent Asylum Hill neighborhood. Clemens was introduced to Twitchell in 1868 by the wife of publisher Elish Bliss, beginning a lifelong friendship between the pair. Twitchell played a significant role in many of the most important events occuring in the Clemens family. He was the presiding clergyman at Sam's marriage with Livy, and at their daughter Clara's wedding with Ossip Gabrilowitsch. Twitchell also provided support during the darkest periods for the family; he was present at the death of Susy, and officiated over the funerals of both Livy and Jean, and well as over Sam's funeral in New York City. During Sam's residence in Hartford, he and Joseph were frequent companions, and belonged to the same social clubs. He had an active influence over Mark Twain's writing, reading manuscripts, and providing ideas and support. As well, the two travelled to Bermuda twice, and it was Twitchell's visit to the Clemenses in Europe in 1878 that provided Twain with the framework needed to write A Tramp Abroad. Twitchell was the model for the Mr. Harris character in that book.
Henry Huttleson Rogers (1840-1909)	Standard Oil Company executive who helped rescue Sam Clemens from bankruptcy. One of the wealthiest industrialists of his time, H.H. Rogers was an admirer of Twain's writings. Upon hearing of Clemens' financial trouble, he came to his assistance after the two met in 1893. Rogers involved himself in all aspects of Clemens' financial woes. He inspected the Paige compositor, and convinced Clemens that it was a failure. He assisted in the bankruptcy of the Charles L. Webster publishing company; he assigned all of Twain's copyrights to Livy Clemens and named her primary creditor. As well, it was his financial plan that Clemens used to pay off his debts. Rogers acted on Clemens' behalf in making a book deal with Harper's in 1903 which made that company Clemens' exclusive American publisher. Besides being his financial guru, Rogers was a close personal friend of Clemens. They were drinking and poker buddies, and Sam would often stay with Rogers at his New York City mansion.