Extracts from History of Routing of NY13 through Ithaca from Wikipedia

"When NY 13 was first assigned, it entered the city of Ithaca on Spencer Road and followed Spencer and Cayuga Streets into downtown. From there, NY 13 proceeded generally northeastward on Court and Linn Streets, University Avenue, and Forest Home Drive through the Cornell University campus to Dryden Road, where it turned eastward toward Dryden.  
  NY 13 was realigned c. 1936 to bypass the Cornell University grounds to the south on State (NY 79) and Mitchell Streets and Ithaca and Dryden Roads. 
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In the early 1960s, a new expressway was built along the eastern shore of Cayuga Lake, bypassing downtown Ithaca on the west and north. NY 13 was altered to follow Meadow Street and the freeway between southwestern Ithaca and the town of Dryden, while the portion of NY 13's old routing that did not overlap NY 79 became an extension of NY 366."