We describe the Information Manifold (IM), a system for browsing and querying of multiple networked information sources. As a first contribution, the system demonstrates the viability of knowledge representation technology for retrieval and organization of information from disparate (structured and unstructured) information sources. Such an organization allows the user to pose high-level queries that use data from multiple information sources. As a second contribution, we describe novel query processing algorithms used to combine information from multiple sources. In particular, our algorithms are guaranteed to find exactly the set of information sources relevant to a query, and to completely exploit knowledge about local closed world information (Etzioni et al. 1994).