Page 454 The Life of Mark Twain: The Early Years, 1835-1871:

Despite his disaffection with the Hookers, when Sam first visited Hartford in January 1868 he was favorably impressed. “I think this is the best built and the handsomest town I have ever seen,” he wrote his Alta readers.  With a population of thirty-seven thousand, the city seemed “to be composed almost entirely of dwelling houses—not single-shaped affairs, stood on end and packed together like a deck of cards, but massive private hotels, scattered along the broad, straight streets, from fifty all the way up to two hundred yards apart. Each house sits in the midst of about an acre of green grass. The city featured “the broadest, straightest streets ... that ever led a sinner to destruction; and the dwelling houses are the amplest in size, and the shapeliest, and have the most capacious ornamental grounds about them.  But I would speak of other things. This is the centre of Connecticut wealth.  Hartford dollars have a place in half the great moneyed enterprises in the Union.” He toured the Colt factory, a collection “of tall brick buildings, and on every floor is a dense wilderness of strange iron machines that stretches away into remote distances and confusing perspectives.” He was particularly interested “in that birth-place of six-shooters,” he wrote his Alta readers, “because I had seen so many graceful specimens of their performances in the deadfalls of Washoe and California.” But he was even more amazed by the new Gatling gun, an early type of repeating artillery weapon, “a cluster of six to ten savage tubes that carry great conical pellets of lead, with unerring accuracy, a distance of two and a half miles” that could be fired “faster than four men can count, ,., It can be discharged four hundred times in a minute! I liked it very much.” The demonstration he observed of the destructive power of the gun became the germ of his inspiration twenty years later for the “Battle of the Sand Belt,” the Armageddon-like conflict that concludes A Connecticut Yankee in King Arthur's Court (“the thirteen gatlings began to vomit death into the fated ten thousand”),”

“Of all the beautiful towns it has been my fortune to see this is the chief. I never saw any place before where morality and huckleberries flourished as they do here” [MTNJ 1: 498].

Mark Twain's home from 1871 to 1891, although he was away almost one third of that time. The family first rented in the Nook Farm are then, in 1873, they purchased property and built a large home where they lived from 1873 to 1891. In 1891 the house was shut down and the Clemenses moved to Europe. The property was sold in 1903 and is now maintained by the Mark Twain Memorial.
Photo: https://www.loc.gov/pictures/item/ct0332.photos.023155p/

Sam was not always so enchanted by Hartford.  In April of 1876 he was concerned with street flooding and wrote two letters to the the Hartford Courant:  "A shocking state of affairs exists in that part of our beautiful city where Niles street used to be. This street is now no more. For some weeks past it has been gradually sinking. Here & there large openings appeared. Gutter stones disappeared, hitching posts unearthed floated in the mire. About a week ago the road became impassable, & since that time the residents not being able to get fresh meat & groceries, have subsisted on codfish, ham, & such salt victuals as they might have had on hand. Some are now out of the necessities of life, & unless a way is found to reach them soon, dreadful results are to be feared."  SLC to the Editor of the Hartford Courant, 5 April 1876, Hartford, Conn. (UCCL 13021). 2022.  and SLC to the Editor of the Hartford Courant, 6 April 1876, Hartford, Conn. (UCCL 13022). 2022

From page 327 The Life of Mark Twain - The Middle Years 1871-1891:

Sam also spoke his mind repeatedly around this time [1880] about a local Hartford issue: polluted water. Ever alert to his civic responsibilities, he had complained about the drainage in the streets as early as 1876 in a pair of pseudonymous letters to the editor of the Hartford Courant, The basements in the homes on Niles Street had flooded, he complained, and nearby lakes had been contaminated with toxic runoff and effluvia from sewers. The next year Sam invested, at Frank Fuller's suggestion, in a still for purifying water, though the device was never built. He occasionally ranted about the decisions by the city fathers that transformed the Park River (formerly the Hog River) into an open sewer and Hartford from “a conspicuously healthy city into a conspicuously unhealthy one.” In September 1880 Sam objected to the quality of water in the Hartford pumps and mains. In an unsent letter to the editor of the Hartford Courant, he alleged that the city was “well stocked with sufferers from malaria” on account of “our bad sewerage & foul & stagnant water courses.’ He modestly proposed to warn visitors to Hartford about the condition of the malodorous water by flying a “black flag with skull & cross-bones” from the dome of the state capitol. The Clemenses stopped drinking the tap water in their home, preferring an imported German mineral water. ...  Sam also tried to address the water issue by contracting with a plumber to fix or replace the pipes in his Farmington Avenue house during the spring and summer of 1880. Coincidentally, the same month the plumbers went to work Sam bought a strip of land along the south boundary of the Hartford property from his neighbor Franklin Chamberlin “& the very next day, just within the bounds of that strip, we struck a spring of cold, sweet, limpid & abundant water,” though it was never pumped into the house.

July 19, 1888 Thursday, Day By Day:   In Elmira Sam wrote to Franklin G. Whitmore, enclosing a letter meant for newspaper publication. The letter is a humorous and scathing sort aimed at the city of Hartford for moving an electric lamp and post on Forest Street. A few of the more cutting excerpts:

...

Sam directed to take the letter to the Hartford Courant, and if they wouldn’t print it “without an alteration” or apologizing for it in an editorial, take it to the Hartford Times; and if that failed, take it to William Mackay Laffan and ask to print it in the New York Sun, complaining he couldn’t get a hearing in Hartford [MTP]. Sam’s “bill of complaints was not published” [MTNJ 3: 404].

While in Munich, Sam wrote a letter to the Hartford Courant about tramps.  Fears notes in the Day By Day entry for February 2, 1879: "Sam wrote from Munich to the editor of the Hartford  Courant, enclosing a Jan. 11 article of that paper that he’d just received. The article was about tramps who had been jailed in Hartford. Sam was gratified that Hartford had “at last ceased to be the Tramp’s Heaven.” He wrote of the positive Munich experience with beggars after giving them work and denying handouts.:  See To the Editor of the Hartford Courant  2 February 1879 • Munich, Germany

See "City of Hartford" Speech, for the Reception for Worcester Continentals at Allyn Hall, Hartford.