Stewart was born in Lisburn, Ireland, and abandoned his original aspirations of becoming a minister to come to New York City in the summer of 1823. He spent a short time teaching before returning to Ireland to receive the money his grandfather had left him, purchase some Belfast linens and laces, and return to New York to open a store.
He was a business genius, and by 1848 he had built a large marble-fronted store on Broadway between Chambers Street and Reade Street, which was devoted to the wholesale branch of his business, and the largest retail store in the world at that time. Stewart also had branches of his company in different parts of the world and owned several mills and factories. Stewart had an estimated annual income of $1,000,000 in 1869.
In March of that year, President Ulysses S. Grant offered him the position of Secretary of the Treasury (after Joseph Seligman had declined it), but he was not confirmed by the Senate due to his close association with Judge Henry Hilton, his wife's cousin's husband and a member of the corrupt Tweed Ring.
Three weeks after his birth, Stewart’s farmer father died of tuberculosis. About two years later Stewart’s mother remarried and followed her new husband to America, leaving Stewart behind to be raised by his grandfather, John Torney.
While raising his only grandson, Torney wanted Stewart to enter The Church of England to become a minister, but Stewart wanted to go to Trinity College. At age seven, Stewart was sent to a village school, and then in 1814 he entered Mr. Neely’s English Academy. In 1816, when Stewart’s grandfather died, he was brought into the home of Thomas Lamb, an Irish Quaker.
When finishing up his formal education at Belfast Academical Institute, he decided to further his knowledge of other cultures by writing to his mother, who was in New York City at the time. The more Stewart kept in touch with his mother, the more he desired to further his life in New York. However, before moving, Lamb insisted that Stewart get some experience in business training and earn money as a grocer in Belfast. Weary of prolonging his stay in Ireland, Stewart agreed to take the position recommended by Lamb and began to work at the age of fifteen as a bag boy. In the spring of 1818, shortly after working as a grocer, Stewart packed his bags along with the $500 he had earned and left Belfast for New York City. After traveling for about six weeks at sea, Stewart arrived at his mother's home in New York City. Upon his arrival in the big city, Stewart became a tutor at Isaac N. Bragg’s Academy, a school for wealthy students located on Roosevelt Street. Here he earned $300 a year, an honest wage during the early 19th century. After securing a place to live and a job, Stewart joined an Episcopalian church run by Reverend Edward Mitchell. There Stewart met his future wife, Cornelia Mitchell Clinch, the daughter of Susannah Banker and Jacob Clinch, director of the New York Customs House.
Upon returning to New York City in 1823, Stewart married Cornelia on October 16, 1823. Before marrying, Stewart opened his first store. Located at 283 Broadway, the first in a series of retail locations Stewart established in his future empire of A.T. Stewart and Company, his store sold Irish fabrics along with some domestic calicos, which had been purchased with money from his inheritance and his earnings as a tutor.
The store was just across from City Hall Park, north of Chambers Street on the opposite side of Broadway from where his later successful store, “The Marble Palace” was to be built. The store opened on September 1, 1823. It measured 12.5 feet wide by 30 feet deep, being a rather small store by today’s standards, but average size during the 19th century. Stewart rented out the space for $375 a year. The store was split up into two parts, divided by a thin wall. The larger front section was used for the business and the smaller area in back served as the owner’s residence.
Unlike his other competitors in the dry goods trade who were located along Pearl Street, Stewart innovated by placing his establishment several blocks west on Broadway. He acknowledged that customers would travel to buy goods where they could get the best price and the easiest method of buying. Stewart knew that the key to success was not where the store was placed, but rather where “to obtain wholesale trade to undersell competitors".
When first opening the store, Stewart placed cases full of merchandise along the sidewalk in front of the store as a way of advertising his establishment. Stewart claimed that “the messy clutter in front of the store and pushing crowds advertised the business.”
As he rose to the top of the retail developers, Stewart included no signs on any place of his store and did not use any advertisements until May 13, 1831. He felt that anyone who wanted to shop in his store would “know where it was located.”
A natural salesman, Stewart realized that “you will deal with ignorant, opinionated and innocent people. You will often have an opportunity to cheat them. If they could, they would cheat you, or force you to sell at less than cost. You must be wise, but not too wise. You must never actually cheat the customer, even if you can.... You must make her happy and satisfied, so she will come back.” Stewart held that the key to establishing a great business was to make friends with the customers and encourage their return.
The three-story building was located at 280 Broadway at the corner of Chambers Street, just across from his first store, and offered imported European women’s clothing. In addition to its merchandise, the second floor offered the first women’s “fashion shows” as full-length mirrors enabled women to view themselves from different angles.
The design, using Tuckahoe marble, encompassed an innovative flair consisting of columns, pillars and corniced windows resembling the Palladian style, reminiscent of Thomas Jefferson’s home. This proved to be the first commercial building in the United States to display an extravagant exterior. Inside, not only did Stewart want to display his merchandise, but he wanted the structure to emphasize natural light from its central rotunda and high ceilings.
“The Marble Palace” claimed to be one of the first “big stores” that sold merchandise, and was a huge financial success. In 1856 Stewart decided to expand his merchandise to include furs, “the best and most natural skins”, as customers were told. In the 1850s, he also followed other retailers such as Macy's, Lord and Taylor and B. Altman and Company to the area which was to be called “Ladies Mile”, on Broadway and Sixth Avenue between 9th Street and 23rd Street. However, in 1862, Stewart’s “true” department store, referred to as the “Iron Palace”, was built. This six-story building with its cast-iron front, glass dome skylight and grand emporium, employed up to 2,000 people. The immense structure resided on Broadway and Ninth Street, near Grace Church. The establishment’s nineteen departments included silks, dress goods, carpets and even toys.
By 1877, Stewart’s new retail establishment had been moved to Tenth Street and Astor Place. It had expanded to thirty separate departments, carrying a wide variety of items. As noted by The New York Times, “a man may fit up his house there down to the bedding, carpets and upholstery.”
Beginning in 1868, Stewart began receiving letters from women in rural parts of the United States requesting his merchandise. Stewart promptly replied to these letters and orders by sending out the requests and even paying the postage. Once received, women would send back the money needed to pay for their orders.
Seeing potential for the mail order business, by 1876 Stewart had hired twenty clerks to read, respond and mail out the entailed orders. That year he profited over $500,000 from the mailing business alone. Stewart’s mail-order business’ efficiency, convenience and profits gained so much attention from all over the country that other famous businesses such as Sears, Montgomery Ward and Spiegel's followed in his footsteps.
In 1869-70, A.T. Stewart built the first of the grand Fifth Avenue palaces, on the northwest corner of 34th Street, across from the doyenne of New York society, Caroline Schermerhorn Astor. His architect, as for the store, was John Kellum. When all of Fifth Avenue was of brownstone rowhouses, Stewart's fireproof structure in French Second Empire taste was faced with marble.
It had three main floors and an attic in a mansard roof. A mezzanine floor at cornice height was used for storage. The house was separated from the sidewalks by a moat-like light well that lit the service areas in the basement. The main parlour ran the full length of the house's Fifth Avenue frontage.
On the death of Stewart's widow in 1886, it was rented as premises for the Manhattan Club and was painted in 1891 by Childe Hassam In 1901 Stewart's marble palace was razed, to make way for the new premises of the Knickerbocker Trust Company.
Stewart incorporated the Central Railroad of Long Island in 1871 and completed it in 1873, running from Long Island City through his development at Garden City to a brick yard at Bethpage and docks at Babylon. This became part of the Long Island Rail Road system in 1876, and the parts that have not been abandoned are the Hempstead Branch and Central Branch.
At the time of his death, Stewart was building at Hempstead Plains, Long Island, the town of Garden City, with the purpose of affording to his employees comfortable and airy housing at a moderate cost. After his death, his wife Cornelia erected several buildings in memoriam, including St. Paul's School and The Cathedral of the Incarnation, Garden City; the latter also served as a mausoleum to both Stewart and his wife. Stewart and his wife had played a large role in the development of Garden City, developing such landmarks as The Garden City Hotel, St. Paul's School and the Cathedral of the Incarnation, all of which still stand today.
Three weeks after his burial at St Mark's Church in the Bowery, Stewart's body was stolen and the remains held for ransom. The ransom was paid, and remains were returned, although never verified as his. A local legend states that the mausoleum holding his remains is rigged with security devices which will cause the bells of the Cathedral to ring if ever disturbed.