In 2016, the New York City Landmarks Preservation Commission launched its Esri-based landmarks map. While it is an enormous improvement over the previous official iteration, inside the NYCity Map, it does have a few drawbacks:

• While it is responsive, you’d need to add https to the url, otherwise it will never find your location on a phone.
• No matter how many times you visit it, you’ll get the welcome overlay. If you click on desktop to recover your location, you’ll get the overlay all over again.
  Some landmarks have the wrong information (Prospect Park has the wrong LP (LP-0901), and if you click on the designation report, it will take you to that of the Grant National Memorial). Also, there’s a mix up of the City & Suburban Homes Company, First Avenue Estate, only the extension is there.
• It has a penchant to renaming landmarks as designated, old or new. For example, the Abigail Adams Smith House was designated as such, but it’s called Mount Vernon Hotel Museum in the map. Also, there is a movement to rename landmarks to add both spouses (the Andrew Carnegie Mansion becomes the Andrew and Louise Carnegie House in the map, for example.) There are dozens of these name changes, which sometimes seem arbitrary. Call me crazy, but the name as mentioned in the official designation report should be used.
• All historic lampposts are excluded.

Having said that, the map is very useful because it has the actual lots of the landmarks and districts. Plus, if you get the https protocol to work on your smartphone, it is very useful to find what’s around you. Lastly, the map appears to be run by LPC staff, which means it updates very frequently, unlike the maps at the NYC Open Data page.