U.S. Route 15 (US 15) is a part of the United States Numbered Highway System that runs from Walterboro, South Carolina, to Painted Post, New York.

[3] US 15 enters New York adjacent to the state line borough of Lawrenceville, Pennsylvania, at which point the northern segment of I-99 begins.

A four-lane freeway through the Steuben County town of Lindley, US 15 crosses through a rock cut, making a large bend to the north and bypassing the hamlet of Presho.

After CR 5, US 15 bent northeast through the town of Erwin, running to the west of the Indian Hills Golf Club.

After CR 107, US 15 enters a large interchange that utilizes several flyover ramps between US 15, I-86, and NY 17 (Southern Tier Expressway).

[8] By 1929, US 111 was assigned, following what had been PA 4 northward from Williamsport, Pennsylvania, to the New York state line at Lawrenceville, where it ended.

[20] In the mid-1960s, work began on a limited-access highway paralleling US 15 from Presho to the Southern Tier Expressway at Painted Post.

One connection, I-86/NY 17 east to North Hamilton Street, was lost in this version due to the ramp setup of the southern half of the interchange.

[citation needed] I-99 currently ends just shy of I-80; however, construction is either underway or has been completed on projects to upgrade US 220 and US 15 between Bellefonte, Pennsylvania, and Corning to Interstate Highway standards.

[citation needed] In June 2007, work began on a new freeway alignment for US 15 between the Pennsylvania state line and Watson Creek Road in Lindley.

[3] While signs for US 15 were removed after the designation of I-99, they were restored in 2016, and US 15 and I-99 continue to officially overlap for the entire length of the routes in New York.