What is now Main Street was originally known as Flower Hill Avenue; the name was changed to Main Street in 1912. 14 years prior to this renaming, the Long Island Rail Road's Port Washington Branch was extended to
its present terminal on the south side of the street; it previously terminated at the
Great Neck station in
Great Neck Plaza. The opening of the Port Washington extension ushered rapid growth along Main Street and across the rest of the Port Washington area and Cow Neck. This trolley line was constructed in 1907 and opened in 1908. The
Port Washington Post Office, located at the northeastern corner of NY 101 and LuEsther T. Mertz Plaza opened one year prior – a project also funded as part of the
New Deal;
WPA murals would also be installed inside the building. In the 1950s, a proposal was made to redevelop the portion of Main Street adjacent to the Port Washington station – and to replace the existing terminal. Under this project, the existing station would have been demolished, with a large, new commercial development being erected along Main Street; a new station facility would have been integrated into the new commercial block along Main Street. In 2018, construction began on improving the road in the vicinity of the LIRR station. In addition to improvements to traffic flow, the project included the creation of improved pedestrian and bicycling facilities along Main Street – along with the installation of brick pavers, greenery, and other beautification work to create a vibrant streetscape. Known as the "Port Promenade Street Fair," this event – similar to an eponymous event on Main Street from the 20th century – would see vendors and restaurants set up pavilions and seating on the road, for use by the public; the designated areas of Main Street, during the event, would be open solely to pedestrians. The event proved popular, and it became an annual tradition. In 2023, the
Port Washington Police District announced that it would relocate its headquarters to a new facility on Main Street. Construction is set to begin in the fall of 2025. Beginning in 1959, when the Nassau County Department of Public Works created a numbered highway system as part of their "Master Plan" for the county highway system, Main Street was designated as part of County Route 15, which ran between
Old Northern Boulevard in
Roslyn and
Manhasset Bay in
Manorhaven. This route, along with all of the other county routes in Nassau County, became unsigned in the 1970s, when Nassau County officials opted to remove the signs instead of allocating the funds to replace them with new ones that met the latest federal design standards and requirements stated in the federal government's
Manual on Uniform Traffic Control Devices. == Major intersections ==