There are/were three [Interstate 86] in the history of the [Eisenhower Interstate System].

The first is in [Idaho], and was created when it was renumbered from [Interstate 15W]. It's a short little thing, connecting [Interstate 15] and [Interstate 84] in a prompt fashion.

The second was another little strip of highway in [Connecticut] and [Massachusetts] between [Hartford, Connecticut] and the [Mass Pike]. It was renumbered as [Interstate 84] when that highway's extension to [Providence, Rhode Island] was cancelled.

The third is [New York] [Route 17] (the [Quickway], and the [Southern Tier] Expressway), which stretches from [Harriman, New York] to near [Erie, Pennsylvania]. [Route 17] was originally built in the 40's and 50's, but not up to Interstate standards. A plan was proposed in the mid 90's to upgrade the highway, and on December 3, 1999, the western portion of the highway received Interstate 86 designation, from Erie to [Corning, New York]. It will take some time for the new number to be put up all the way east to Harriman, as a lot of reconstruction will need to take place, specifically in [Horseheads, New York|Horseheads], [Hancock, New York|Hancock], and [Parksville, New York|Parksville].

Interstate 86 (thing)