Livingston and Ontario Counties NY 15A begins at an intersection with
NY 15 in the town of
Springwater hamlet of the same name, also officially known as Springwater Hamlet, located on the east side of a large valley in southeastern
Livingston County. The route heads northward as North Main Street, proceeding along the eastern base of the valley as it passes through the northern half of the community. Outside of the
hamlet, NY 15A enters a rural, undeveloped area dominated by dense forests to the east and a low-lying, slightly more open area to the west. As the route approaches the Livingston–
Ontario county line, the lowlands give way to marshes, which in turn lead to
Hemlock Lake at the county line. While in Ontario County in the town of
Canadice, NY 15A follows a more inland route to the east, passing through an isolated forest situated between Hemlock and
Canadice Lakes. After , the highway reenters Livingston County near the northern end of Hemlock Lake. Now in the
town of Livonia, NY 15A becomes Bald Hill Road as it passes by Hemlock Lake Park, a local park situated at the northeastern tip of the lake. It changes names again just later upon entering the hamlet of
Hemlock. Here, it becomes Main Street and intersects
US 20A, which forms a
concurrency with NY 15A along the length of Main Street. The concurrency continues through Hemlock and into rural Livonia, where the overlap ends as US 20A turns west towards
Buffalo. NY 15A, meanwhile, heads northward into the
town of Lima as Plank Road. It continues across rural terrain for another to the
village of Lima, where it becomes Lake Avenue. At the village center, NY 15A crosses over
US 20 and
NY 5 and changes names to Rochester Street. The route leaves the community and its residential surroundings after , but retains the Rochester Street name until it reaches the Livingston–
Monroe county line west of
Honeoye Falls.) at an intersection to the northwest. Past Monroe Street, the route makes a long, significant turn to the west, following
Honeoye Creek into the town of
Rush and the hamlet of the same name. The highway meets Rush–West Rush Road at an intersection south of the community, at which point NY 15A turns back to the north and crosses over Honeoye Creek. In the process, NY 15A becomes East Henrietta Road, a name the highway retains until its northern end in
Rochester. On the opposite side of the creek, NY 15A intersects
NY 251 in the center of Rush. Outside of Rush, NY 15A takes on a more northeasterly alignment as it passes Rush's town reservoir and enters the town of
Henrietta. The surroundings initially remain as rural as they were in Rush; however, the amount of development along the highway gradually increases as the route approaches and passes over the
New York State Thruway (
I-90). One mile (1.6 km) later, NY 15A intersects
NY 253 in a densely populated area west of
Rush–Henrietta Senior High School. The homes continue for another to the Monroe County Fairgrounds (home to
The Dome Center), at which point NY 15A begins to become lined with commercial establishments. The trend temporarily ceases around an interchange with
I-390—where NY 15A curves northwestward—but resumes ahead of a junction with
NY 252, itself a major commercial strip. North of NY 252, NY 15A passes under the
CSX Transportation-owned
West Shore Subdivision and crosses into
Brighton. Just past the town line, the route connects to Clay and Brighton–Henrietta Town Line Roads by way of a grade-separated intersection north of the railroad overpass. It continues onward, passing along the west side of the sprawling
Monroe Community College campus to another interchange with I-390. NY 15A passes over the
Erie Canal and enters the city of Rochester shortly afterward. Once in the city, the route passes by two large office campuses south of Westfall Road and several blocks of homes north of the street before merging back into NY 15 (Mount Hope Avenue) at a junction east of
Strong Memorial Hospital. ==History==