Abstract: Over the spring and summer of 2014, New York City put in place a full-day universal pre-kindergarten (UPK) program. The blistering pace, enormous scale, and administrative complexity of this rollout were all striking: a program that did not exist when funding for it was finalized in March 2014 had put 53,250 four-year-olds in more than 1700 new full-day programs by the first day of school in September. This report provides a detailed account of the launch. It includes an extensive discussion of the city’s use of data science techniques; the city was able to combine and analyze databases in such a way that outreach teams could contact households that were likely to include four-year-olds and help interest parents sign up, all with a sharp eye for the privacy of New Yorkers. The launch as a whole combined the energy of a micro-targeted political campaign with service-oriented, street-level energy, and the lessons New York City learned in the course of this work should be useful to other cities and states.