The NYC GIS Meetup will be held at The Wall Street Journal office on March 12th, and it's an opportunity for attendees to learn about the pros and cons of using custom maps instead of Google Maps. Sebastian Delmont from StreetEasy will discuss his company's experience with creating its own maps based on OSM data and a custom tileset served by Mapbox. Additionally, other project participants will share their experiences with web mapping tools like CartoDB, offering attendees a diverse range of perspectives on the topic. The event is open to anyone interested in GIS and cartography.