As of October 2024, Street View, Then & Now: New York City's Fifth Avenue will no longer be updated by NYPL and will soon be archived.
Source code for the site can be viewed here: https://github.com/nypl-publicdomain/fifth-avenue
and the digitized Fifth Avenue, New York, From Start to Finish collection can be viewed here: https://digitalcollections.nypl.org/collections/fifth-avenue-new-york-from-start-to-finish.
The New York Public Library A public domain remix by Bert Spaan of NYPL Labs, using the Fifth Avenue from Start to Finish collection. View source code.