since how may years is the route being used?
113 years (since 1908)
New York State Route 12D
In 1908, the New York State Legislature created Route 27, an unsigned legislative route that initially extended from Forestport to Alexandria Bay via Boonville, Lowville, and Watertown. From Boonville to Lowville, Route 27 utilized what is now NY 12D and NY 26.
which places are connected by new york state route 12d? Oneida County village of Boonville; and Lewis County village of Lyons Falls.
wiki:8780551
New York State Route 12D [SEP] History
Instead, NY 337 was initially extended eastward along the former alignment of NY 12 on McAlpine Street to a new terminus at Center Street. It was rerouted east of Cherry Street to follow Cherry south to NY 12 . The former routing of NY 337 along McAlpine Street from Cherry Street to a grade crossing with the Mohawk, Adirondack and Northern Railroad, a distance of , is now designated as NY 970J, an unsigned reference route. The overlap between NY 12D and NY 26 north of Potters Corners was eliminated when NY 12D was rerouted to follow NY 337 to Lyons Falls, placing NY 12D on its current alignment.