The City of New York’s health department has, since last November, been mapping the city’s rat population in an effort to get a better handle on its rodent control efforts. Time has an article:

Today, rodent complaints by residents from all over New York are electronically pinpointed on the city’s computerized rat map, which allows inspectors to track complaints and hot spots over time and determine how well rat-control efforts are working. The results, after just one year, should be music to the ears of most New Yorkers: when the pilot study began in the Bronx, inspectors found active rat signs on 3,100 of the borough’s 39,000 properties. Preliminary results now show that 1,250 of those properties are rat-free. That’s a 40% drop-off in infestations.

The map itself can be accessed via the city’s Rat Information Portal; you may have some issues accessing it, and the interface is familiarly clunky. Via Cartophilia, among others.