It was moved onto its current alignment to Croton Lake in the late 1930s, but the easternmost piece was designated as an extension of NY 129 to a traffic circle in the hamlet of Pines Bridge.

It heads westward as Saw Mill River Road, following the northern edge of the reservoir for 1 mile (1.6 km) to an intersection with NY 129.

The contract on SH 148, 3.48 miles (5.60 km) long, was completed August 5, 1905 at the cost of $34,272.91 (equivalent to $1.12 million in 2025), half paid by the state.

[4] NY 118 was assigned as part of the 1930 renumbering of state highways in New York; however, it did not initially follow any of its modern alignment.

At the time, NY 100 continued north along Baldwin Place Road and Myrtle Avenue to meet then-US 6 near Mahopac Falls.

[2] In June 1934, the portion of NY 118 between Somers and Croton Falls became concurrent to US 202, a new interstate route extending from Delaware to Maine.