The South County Trailway is a paved bicycle and pedestrian trail that extends from the Bronx line at Van Cortlandt Park to Elmsford (where, after a brief gap, it continues as the North County Trailway). Both trailways sit on the right-of-way of the long-abandoned Putnam Division of the New York Central Railroad, known affectionately as "The Old Put."
At the southern end of the South County Trailway, the pavement ends, but the trail continues straight through Van Cortlandt Park to (you guessed it) Putnam Avenue. If you take it this far, you'll be near the old Stella D'oro bakery, which was one of the last companies to utilize sections of the Putnam Line for movement of freight.
The closest access to the trail can be found at the waypoint below. Parking in the area is a bit tricky, especially between April 1 and October 31, when parking north of Alan B. Shepard Place is by permit only. Please pay attention to alternate side parking restrictions as well.
At 5'8", I placed this cache just at the upper limit of my vertical reach (hence the extra 1/2 terrain point). Children will need assistance from adults, and shorter adults may need something to stand on. This cache sits in its hiding place, but is not wedged or otherwise secured, so I'm starting it with a small bit of duct tape to prevent it from blowing away. Please do your best to replace as found.
Congrats to Behistun and Navigator on the FTF.