The highway north of Guide Board Corners was once a dual concurrency with the decommissioned New York State Route 330. Route 330 was assigned in the 1930s and remained intact until 1980 when it was decommissioned in favor of a county-maintained highway. After the decommissioning, Route 115 remained intact and has been in place ever since.
CR 115 is surrounded by mountains outside Speedsville. The peaks in this area reach as high as . At the intersection with Yaple Road, the route turns to the east, leaving Boyer Creek behind. The highway passes higher peaked mountains and enters the hamlet of Caroline Center. Route 115 leaves Caroline Center after intersecting a few local roads, and heads to the northeast into Guide Board Corners. There, the original Route 330 began and the highway changes names from Old 76 Road to Central Chapel Road.
It heads then to the north, intersecting with local roads. The highway turns to the west at an intersection with a connector to State Route 79 and changes names to Valley Road. By this point, Route 115 has already left Guide Board Corners and parallels the Sixmile Creek into Brooktondale. There, after crossing Sixmile Creek, the road becomes known as Brooktondale Road. Route 115 continues parallelling the creek the rest of the way. The highway begins climbing a mountain, terminating at an intersection with Route 79.
Routes in Tompkins County are unsigned, although the Tompkins County Highway Division website shows them using the standard County Route shield. Recently, Tompkins County started posting the county roads with the blue pentagon signs.
Route 115 was assigned in the mid-1930s from the Tioga County line to NY 79. Route 115 north of Guide Board Corners, a hamlet of Caroline Township, was also designated New York State Route 330. Route 330 was not state-maintained because of this, instead was maintained by Tompkins County. Route 330 remained intact until January 24, 1980, when during a large maintenance swap between the state of New York and Tompkins County, Route 330 was decommissioned. The CR 115 designation remained in place and is in place to this current date.
In June 2006, the Tompkins County Highway Division closed off Route 115 from Central Chapel Road to Caroline Center. This was because of water damage on the road. All traffic was detoured onto West Creek Road, which connects to Route 79 in Speedsville. The road was repaired for a time afterward.