NY 434 is the former route of NY 17 prior to the construction of the Southern Tier Expressway (STE), which NY 434 parallels. The portion of the expressway from Owego to Johnson City opened in 1969, at which time NY 17 was realigned to follow the STE from Owego to Vestal and NY 17's former routing between the two locations was redesignated as New York State Route 188. However, in October 1969, NY 188 was renumbered to NY 434 as the New York State Department of Transportation believed that the 188 designation would lead to confusion with the then-future Interstate 88 (I-88) northeast of Binghamton. One month later, the portion of former NY 17 between Owego and the Tioga–Broome County line was removed from the state highway system.