Petabytes of Earth science data have been accumulated through space- and air-borne Earth observation programs during the last several decades. The data are valuable both scientifically and socioeconomically. The value of these data could be further increased significantly if the data from these programs can be easily discovered, accessed, integrated, and analyzed. The Global Earth Observation System of Systems (GEOSS) is addressing this need. In particular, the GEOSS Component and Service Registry maintains the descriptive information about available Earth Observation resources that are self-nominated by providers. This registry provides the following capabilities for data providers: user registration, resource registration, and service interface registration. It enables data users to discover these resources through the dedicated graphical user interfaces. It also exposes machine-to-machine interfaces to other GEOSS core components. The captured functional requirements, system design and implementation details of this registry are introduced in this paper, followed by the analysis of the registered resources and the system accessing information. The discussion on the strengths of this registry, the limitations in its current form, and the lessons learned from the system maintenance and upgrade over the last five years may be useful to others building a centralized managed resource catalog to enable a large-scale integrated system following a system-of-systems approach.