Standing at a height of 81 feet (25 meters) above Manhasset Bay and measuring 679 feet (207 meters) in length, the Manhasset Viaduct is the highest bridge on the entire LIRR network.

[3][4][5][6] The Manhasset Viaduct is a critical component of the infrastructure on the LIRR's Port Washington Branch.

[1] Its construction enabled the railroad line to traverse the Manhasset Valley and Manhasset Bay: due to the surrounding area's geographical and topographical characteristics, the LIRR could not extend the line into Manhasset and Port Washington – both communities being located across the valley, on the Cow Neck Peninsula – without it building a viaduct over it and the bay.

[4][5][3] In 1913, the remainder of the Port Washington Branch between the line's split with the former Whitestone Branch east to Port Washington – including the portion of the line over this bridge – was electrified with a third rail, thus enabling electric trains to operate along the entire line; the electrification officially took place on October 21 of that year.

[8] The Manhasset Viaduct is eligible for listing on the National Register of Historic Places, due to its historical and architectural significance and ties to the Carnegie Steel Company.