  We present the Gravitational Wave Treasure Map, a tool to coordinate,
visualize, and assess the electromagnetic follow-up of gravitational wave (GW)
events. With typical GW localization regions of hundreds to thousands of square
degrees and dozens of active follow-up groups, the pursuit of electromagnetic
(EM) counterparts is a challenging endeavor, but the scientific payoff for
early discovery of any counterpart is clear. With this tool, we provide a
website and API interface that allows users to easily see where other groups
have searched and better inform their own follow-up search efforts. A strong
community of Treasure Map users will increase the overall efficiency of EM
counterpart searches and will play a fundamental role in the future of
multi-messenger astronomy.
