The Flushing and North Side Railroad was a former railroad on Long Island built by Conrad Poppenhusen as a replacement for the former New York and Flushing Railroad. The railroad was established in 1868, was merged with the Central Railroad of Long Island in 1874 to form the Flushing, North Shore and Central Railroad, and was finally acquired by the Long Island Rail Road in 1876. Today the main line is known as the Port Washington Branch of the Long Island Rail Road.

Flushing citizens, feeling they had been tricked into building the Flushing and Woodside in order to scare the Flushing and North Side into selling out to the LIRR, convinced wealthy residents of College Point and Whitestone, including Conrad Poppenhusen, to incorporate the Flushing and North Side Railroad on April 3, 1868. This company had the right to build a line from Long Island City to Flushing and beyond to Roslyn, with a branch from Flushing to Whitestone. The group gained control of the unfinished Flushing and Woodside Railroad, and opened its line to Flushing, paralleling the LIRR from Long Island City to Woodside, in 1868^[10] and to College Point and Whitestone in 1869.^[11] This new line attracted most of the traffic from the older New York and Flushing, and the LIRR wanted to get rid of its Flushing branch.

In 1869, an affiliate of the Flushing and North Side, the Whitestone and Westchester Railroad, built the Whitestone Branch. It was intended to cross the East River to Westchester County, but never had the chance to do so. The line had a spur to a freight dock on Flushing Bay which crossed the Woodside Branch and the connecting line between the Woodside and Whitestone Branches. After the Flushing Bay Freight spur, the line itself also crossed the Woodside Branch, and then merged with the Woodside-Whitestone connector before crossing the Flushing River. From there it contained four stations, one at Bridge Street, College Point, and two in Whitestone, one at 14th Avenue and the other at 155th Street, which has been called Whitestone Landing station, and Beechhurst Yacht Club station. Malba station was not built until decades after the line was acquired by the LIRR.

In 1869, the New York State Legislature authorized the Flushing and North Side to buy the New York and Flushing east of the LIRR crossing at Winfield Junction^[12] connections were built by the Flushing and North Side at Woodside/Winfield and Flushing to connect its lines. The New York and Flushing continued to own the line west of Winfield, and soon became the South Side Railroad's access to Long Island City.

The segment between what was to become the former Laurel Hill and Winfield Junction stations was abandoned for passenger service in 1875, and completely abandoned in 1880. Part of the right-of-way ran through what is today the Mount Zion Jewish Cemetery in Maspeth.^[13] The Flushing and Woodside was merged into the Flushing and North Side in 1871, and its line was abandoned in favor of the ex-New York and Flushing line.^[9][14]

Since both the NY&F and F&NS planned to expand service east of Great Neck, subsidiaries of the railroad were created for this purpose. In the case of the F&NS, two proposed railroads included the North Shore and Port Washington Railroad and the Roslyn and Huntington Railroad. Neither of these proposals were carried out. In fact, they were eliminated during the merger with the Central Railroad of Long Island in 1874 (see below), although the LIRR did try to extend the line to Roslyn until 1882 due to the difficulty of construction around the Manhasset Valley.

On June 19, 1874, all branches of the Flushing and North Side Railroad, including the Main Line to Great Neck were incorporated into the Flushing, North Shore and Central Railroad, which included the Central Railroad of Long Island. Two years later, it would become part of the Long Island Rail Road. Despite the failed attempt to extend the line from Great Neck to Roslyn in 1882, wealthy Port Washington residents persuaded the LIRR to bring the terminus to their hometown in 1895. This required the construction of the Manhasset Viaduct over Manhasset Bay, which was completed on June 23, 1898. The Woodside and Whitestone Branches were abandoned.