A Brief History:
The Long Island Railroad had its beginnings in 1832, with the chartering of the Brooklyn & Jamaica Railroad Company. The Brooklyn & Jamaica was to be a 10-mile line extending eastward from the Brooklyn waterfront (near the present-day Manhattan Bridge) along Atlantic Avenue to a terminal at Sutphin Boulevard in Jamaica.
The primary force behind the Brooklyn & Jamaica was Major D.B. Douglass, who envisioned it as part of a rail-and-ferry connection between New York City and Boston.
The Long Island Railroad was chartered in 1834 to connect Jamaica with Greenport, on the East End of Long Island. From Greenport, a ferry would run to Stonington, Connecticut, and a railroad called the Norwich & Worcester would continue on to Boston.
In 1836, the LIRR took over the original Brooklyn & Jamaica trackage. Rails reached Hicksville in 1837, Farmingdale in 1841, Deer Park in 1842, and the line was completed to Greenport by the summer of 1844.
The LIRR enjoyed prosperity until 1850, when the New York, New Haven & Hartford built an all-rail connection between Boston and New York. The more roundabout LIRR route was rendered obsolete.
The LIRR, to provide the quickest possible service between Brooklyn and Greenport, had run its tracks directly down the island's center, which was mostly uninhabited at the time. The LIRR was slow to build branch lines to the larger towns on either shore, and so a number of competing railroads sprang up.
The Central of Long Island operated between Flushing and Bethpage, running in a southeasterly direction. Most of it was abandoned and sold to the New York City Parks Department as the Kissena Corridor. Only a short leg of the Hempstead Branch is still in operation.
The South Side & Jamaica connected Williamsburg, Brooklyn, and Patchogue, and is operated as today's Babylon Branch, Rockaway Branch, West Hempstead Branch, and Bay Ridge Branches.
The Flushing & North Side was the LIRR's strongest competitor. It was owned by College Point businessman Conrad Poppenhusen, and operated over today's Port Washington Branch, and also over the abandoned Whitestone Branch.
The Flushing & North Side swallowed all of its competitors in the 1870s, lastly the Long Island Railroad, in 1875. The Long Island Railroad name, however, was retained.
The united LIRR was immediately in a financial bind. Duplicate trackage was abandoned, but the railroad went into receivership in 1877. The railroad re-emerged and thrived under the strong leadership of Austin Corbin, who died in 1896 just as his plans to turn the eastern terminus of Montauk into a deepwater port were near completion. Had this happened, nearly a day of travel time would have been shaved off of shipping into New York City, and the railroad's profitability would have been ensured for years to come.
The LIRR came under control of the Pennsylvania Railroad in 1910. The PRR built the tunnel under the East River to Penn Station, which became the LIRR's western terminal. The LIRR was operated as a subsidiary of the Pennsylvania until 1950. By 1950, the LIRR was losing money for its parent railroad, and the generally deteriorating profits, industry-wide, meant that the PRR could not afford to hold onto the LIRR.
The railroad staggered on for a few years, going in and out of receivership, and finally came under control of the MTA in 1966.
Source: "Steel Rails to the Sunrise", by Ron Ziel and George Foster, Hawthorn Books, 1965.