Jay Gould

Gould's school principal was credited with getting him a job as a bookkeeper for a blacksmith. A year later, the blacksmith offered him half interest in the blacksmith shop, which he sold to his father during the early part of 1854. Gould devoted himself to private study, emphasizing surveying and mathematics. In 1854, he surveyed and created maps of the Ulster County, New York, area. In 1856, he published History of Delaware County, and Border Wars of New York, which he had spent several years writing.

In 1856, Gould entered a partnership with Zadock Pratt to create a tanning business in Pennsylvania in an area that was later named Gouldsboro. He eventually bought out Pratt, who retired. In 1856, Gould entered a partnership with Charles Mortimer Leupp, a son-in-law of Gideon Lee and one of the leading leather merchants in the United States. The partnership was successful, until the Panic of 1857. Leupp lost all his money in that financial crisis, but Gould took advantage of the depreciation in property value and bought up former partnership properties.

In 1859, Gould began speculative investing by buying stock in small railways. His father-in-law Daniel S. Miller introduced him to the railroad industry by suggesting that Gould help him save his investment in the Rutland and Washington Railroad in the Panic of 1857. Gould purchased stock for 10 cents on the dollar, which left him in control of the company. He engaged in more speculation on railroad stocks in New York City throughout the Civil War, and he was appointed manager of the Rensselaer and Saratoga Railroad in 1863.

The Erie Railroad encountered financial troubles in the 1850s, despite receiving loans from financiers Cornelius Vanderbilt and Daniel Drew. It entered receivership in 1859 and was reorganized as the Erie Railway. Gould, Drew, and James Fisk engaged in stock manipulations known as the Erie War, and Drew, Fisk, and Vanderbilt lost control of the Erie in the summer of 1868, while Gould became its president.

He married Helen Day Miller (1838–1889) in 1863; the couple had six children:

Gould married Helen Day Miller (1838–1889) in 1863; they had:

It was during the same period that Gould and Fisk became involved with Tammany Hall, the Democratic Party political machine that largely ran New York City at the time. They made its boss, William M. Tweed, a director of the Erie Railroad, and Tweed arranged favorable legislation. Tweed and Gould became the subjects of political cartoons by Thomas Nast in 1869. Gould was the chief bondsman in October 1871 when Tweed was held on $1 million bail. Tweed was eventually convicted of corruption and died in jail.

In August 1869, Gould and Fisk began to buy gold in an attempt to corner the market, hoping that the increase in the price of gold would increase the price of wheat and motivate western farmers to sell. This, in turn, would cause a great amount of shipping eastward, increasing freight business for the Erie Railroad. During this time, Gould used contacts with President Ulysses S. Grant's brother-in-law Abel Corbin to influence the president and his Secretary General Horace Porter. These speculations culminated in the panic of Black Friday on September 24, 1869, when the premium over face value fell on a gold Double Eagle from 62 percent to 35 percent. Gould made a small profit from this operation by hedging against his own attempted corner as it was about to collapse, but he lost it in subsequent lawsuits. The gold corner established Gould's reputation in the press as an all-powerful figure who could drive the market up and down at will.

In 1873, Gould attempted to take control of the Erie Railroad by recruiting foreign investments from Lord Gordon-Gordon, supposedly a cousin of the wealthy Campbell clan who was buying land for immigrants. He bribed Gordon-Gordon with a million dollars in stock, but Gordon-Gordon was an impostor and cashed the stock immediately. Gould sued him, and the case went to trial in March 1873. In court, Gordon-Gordon gave the names of the Europeans whom he claimed to represent, and he was granted bail while the references were checked. He immediately fled to Canada, where he convinced authorities that the charges were false.

After being forced out of the Erie Railroad, Gould started to build up a system of railroads in the midwest and west. He took control of the Union Pacific in 1873 when its stock was depressed by the Panic of 1873, and he built a viable railroad that depended on shipments from farmers and ranchers. He immersed himself in every operational and financial detail of the Union Pacific system, building an encyclopedic knowledge and acting decisively to shape its destiny. Biographer Maury Klein states that "he revised its financial structure, waged its competitive struggles, captained its political battles, revamped its administration, formulated its rate policies, and promoted the development of resources along its lines."

By 1879, Gould gained control of three more important western railroads, including the Missouri Pacific Railroad. He controlled 10,000 miles (16,000 km) of railway, about one-ninth of the rail in the United States at that time, and he had controlling interest in 15 percent of the country's railway tracks by 1882. The railroads were making profits and set their own rates, and his wealth increased dramatically. He withdrew from management of the Union Pacific in 1883 amid political controversy over its debts to the federal government, but he realized a large profit for himself. He obtained a controlling interest in the Western Union telegraph company and in the elevated railways in New York City after 1881. In 1889, he organized the Terminal Railroad Association of St. Louis which acquired a bottleneck in east–west railroad traffic at St. Louis, but the government brought an antitrust suit to eliminate the bottleneck control after Gould died.

Gould died of tuberculosis, then referred to as "consumption," on December 2, 1892, and was interred in the Woodlawn Cemetery, The Bronx, New York. His fortune was conservatively estimated for tax purposes at $72 million (equivalent to $1,886,000,000 in 2019), which he willed in its entirety to his family.

At the time of his death, Gould was a benefactor in the reconstruction of the Reformed Church of Roxbury, New York, now known as the Jay Gould Memorial Reformed Church. It is located within the Main Street Historic District and listed on the National Register of Historic Places in 1988. The family mausoleum was designed by Francis O'Hara.