NY 25A's street name in Nassau County, particularly regarding the eastern half of the county. While signage for Northern Boulevard exists as far east as Cold Spring Road, implying that Northern Boulevard extends from Queens to the Suffolk line, several businesses located between NY 107 and NY 106 give North Hempstead Turnpike as the highway's name. Additionally, an old, undated Hagstrom Map from the late 1940s indicates that the Turnpike name extends as far west as the Queens line. Suffolk County NY 25A makes a sharp northward turn just inside the county line at an intersection with NY 108. It travels through Cold Spring Harbor, where it is initially called Harbor Road, and then Main Street, before curving back to the east and heading into downtown Huntington. In the hamlet, the road widens to four lanes and is also known as Main Street. At an intersection with County Route 35 (CR 35) on the east side of Huntington, NY 25A narrows to two lanes once more and heads toward Centerport, where it becomes Fort Salonga Road. This name remains in place through Centerport, Northport and Fort Salonga to the vicinity of Sunken Meadow State Park. Just south of the park, NY 25A intersects with its first limited-access highway since the Cross Island Parkway in Queens when it encounters the northernmost exit on the Sunken Meadow State Parkway. Past the parkway, the route changes names from Fort Salonga Road to Main Street as it enters Kings Park, home to the now-closed Kings Park Psychiatric Center. The similarly numbered New York State Bicycle Route 25A (NY Bike Route 25A) joins NY 25A here, switching from CR 11 to NY 25A at the former's east end in the center of the hamlet. NY 25A continues on an eastward track to San Remo (just east of Kings Park), where it makes a sharp southward turn at an intersection with St. Johnland Road in the center of the community. The route takes on the St. Johnland Road name and loosely parallels the Nissequogue River as it heads toward Smithtown. They cross just west of the Village of the Branch at the Smithtown Bull, where NY 25A intersects with its parent route. NY Bike Route 25A ends here; however, NY 25A continues east into the hamlet of Smithtown by way of an overlap with NY 25 along Jericho Turnpike. The Jericho Turnpike name ends a short