The Paige Compositor was an automatic–typesetting machine invented by James W. Paige. Little is known about the inventor of the Paige Compositor. James W. Paige was born in upstate New York in January 1842. While living in Rochester, he applied for his first patent on a typesetter in 1872, and the patent was granted in 1874. He then moved to Hartford between 1874–77 to work for the Farnham Type–Setter Company, which was trying to put together a workable typesetter by combining the gravity-fed Farnham machine with the Thompson distributor. The Farnham Type–Setter Company rented space for about five years at the Colt Firearms factory. The rest of Paige's life centered around the Paige Compositor, trying to market it and make it work. Paige eventually died in the poorhouse, but no one knows where or when.

Twain's love for technology and his background in printing led him to invest in the compositor. Between 1880 and 1894 he invested a fortune into its development, resulting in his near bankruptcy. In an 1889 letter to his brother Orion, Twain writes,

"All the other inventions of the human brain sink pretty nearly into commonplaces contrasted with this awful mechanical miracle. Telephones, telegraphs, locomotives, cotton gins, sewing machines, Babbage calculators, Jacquard looms, perfecting presses, Arkwright's frames – all mere toys, simplicities! The Paige Compositor marches alone & far in the lead of human inventions."

Though the Paige Compositor was faster than the Linotype, its 18,000 parts were prone to malfunction. Paige's invention exhibited superior technological achievement, but its price and temperamental nature made it unattractive to a business world that had already embraced the Linotype. Still, it is regarded today as one of the finest examples of nineteenth century mechanical engineering.

The Clemenses closed their Hartford home and headed for Europe in 1891, in part because of the financial strain of Twain's unprofitable investment.

• Overall Dimensions:
o Height –84"
o Length – 136"
o Width – 43"
o Gross Weight – 7,550 pounds

• 18,000 moving parts made the compositor a complicated machine
• When Mark Twain first saw the compositor, it could set type four times faster than by hand –about 3,000 "ems" (the common measure for a typesetter) an hour versus 750 by hand. At the end of his involvement it could set type at 12,000 ems/hour, or 16 times faster than by hand.
• Two working models were made but, after failing in pre–production tests, the Paige typesetter never went into production.
• One model was given to Columbia University, which later donated it to the scrap metal drive during World War I.
• The other model was at the Cornell University Museum from 1894–1897.
• The Mergenthaler Company bought this compositor for $20,000 in 1897.
• This machine (now the only one in existence) was originally loaned to the Mark Twain House in 1958 by the Mergenthaler Linotype Company of Brooklyn, NY. They donated the machine in 1964. 

It was installed as a single unit in the basement of the Mark Twain House on December 17, 1958. (It has never been taken apart for fear that its 18,000 moving parts could not be put back together again.)

• Twain's initial $2,000 investment occurred around 1880. He inspected the machine as it was being built by Paige at Colt's Patent Firearms factory in Hartford. After seeing the machine perform, he invested an additional $3,000 in stock. Twain wrote to Charles Webster on Oct. 26, 1881 that the $5,000 was "...best investment I ever had. I want an opportunity to add to it -- that is how I feel about it."
• On July 28, 1885, he wrote again to Charles Webster about getting a company in Boston to make and hire out machines at $2,500 each. He thought that eight machines would "do the New York Sun's work and reduce its composition bills from $80,000 per year to $25,000."
• In 1885, Paige asked and received from Clemens an additional $30,000 to make additional improvements to the machine to automatically justify lines. They moved the machine to Pratt & Whitney so Paige could work on it.
• By 1887, with the $30,000 gone and competition from the Mergenthaler Linotype (in use at the New York Tribune), Paige sought additional capital. Clemens, fearing he'd lose all of his money if he withdrew, put $3,000 to $4,000 a month into Paige's typesetter. By 1888, Twain had invested $80,000 and Paige was constantly saying that the machine would be ready in 2–3 weeks.
• On January 5, 1889, the machine worked for the first time, but soon broke down and had to be fixed. In 1890, a group of prospective customers came to see a demonstration of the machine. Nevada millionaire Senator J.P. Jones was ready to invest $100,000, if the machine worked as well as promised. It collapsed as the potential investors arrived.
• Between 1890–91, Twain invested at least $4,000 a month until in 1891, he finally called an end to his involvement in funding of the Paige Typesetter. Twain estimated that his entire investment was around $150,000; his biographer A.B. Paine set the figure closer to $190,000, and William Dean Howells estimated $300,000.
• In June 2003, The Mark Twain House & Museum purchased a manuscript, ca. 1880-90, in which Twain tried to calculate the most economical use of the typesetting machine to be used by his publishing company and a newspaper. He estimated that the machine would have to be in use for almost 24 hours a day in order to afford having it.