It runs north–south as Port Washington Boulevard from NY 25A in Flower Hill, west of Roslyn and east of Manhasset, to Astor Lane in Sands Point.

Just inside of the community, CR 101 intersects Hilldale Drive and Dogwood Road, two local streets connecting to Herricks Middle School.

The route continues on through Searingtown into the village of North Hills, where the homes give way to trees as it turns to the northeast and passes under the Northern State Parkway.

[4] North of the Long Island Expressway, CR 101 passes by Christopher Morley Park to the east and residential neighborhoods to the west.

Past the park, CR 101 enters an area with more residential development as it begins to run along the western boundary of Roslyn Estates and the eastern edge of Manhasset.

[4] In Port Washington, NY 101 passes Nassau Knolls Cemetery and narrows to become a four-lane undivided highway as it enters the center of the hamlet.

It proceeds north–south through downtown, passing several blocks of commercial buildings and Paul D. Schreiber Senior High School ahead of a junction with Main Street.

NY 101 ends shortly afterward at an intersection with Astor Lane, at which point Port Washington Boulevard is continued by Middle Neck Road and designated as CR 101.

North of the club, the highway curves to the northwest and becomes surrounded by several blocks of residential homes to the southwest and patches of trees to the northeast as it heads deeper into the village.

[10][11][12] This project, which began in early 1957, saw the widening of Port Washington Boulevard – most notably the 1.5-mile (2.4 km) part running through Flower Hill, and was carried out by a private firm contracted by the Department of Public Works.

Many people residing in Flower Hill and other surrounding communities were concerned by these improvements, in part due to the number of trees that were removed to accommodate the widened roadway, and the fact that the state did not immediately commit to replanting greenery and restoring the landscape.

[14] This expressway would have extended from Sunrise Highway (NY 27) in Valley Stream north to an intersection with Middle Neck Road (then-CR 101) in Sands Point.

[17] However, other documents produced by NYSDOT, such as their official description of routes in New York, give the highway's northern terminus as Astors [sic] Lane.

[18] In 2014, as part of a project to improve electricity transmission in the area, PSEG Long Island erected a new power line between Great Neck and Port Washington.

[21] Regan, a Purple Heart recipient from Manhasset, was killed on active duty in Northern Iraq on February 9, 2007, when the vehicle that he was in was targeted by an IED.

[26] In the early 20th century, the Port Washington Line of the New York & North Shore Traction Company ran along Middle Neck Road.