Inspired by Esri's GeoEnrichment services and the Linked Data cloud, KnowWhereGraph starts with the concept of geo-enrichment, augments it with Semantic Web and knowledge graph (KG) technology, and proposes the idea of KG-based geo-enrichment, which aims to semantically enrich a given geospatial dataset with information from a cross-domain, up-to-date (geographic) knowledge graph, namely KnowWhereGraph, from within a GIS. Compared with Esri's GeoEnrichment, our KG-based geo-enrichment has several advantages. KnowWhereGraph, supported by Semantic Web technology, is structured in a semantic-explicit manner. Users can easily interpret the meaning of a place type or other vocabulary, including relations, and access additional information and metadata about a (geographic) entity by dereferencing their URLs. That is, this semantic-explicit graph provides users with "things not strings". Additionally, due to the flexible nature of our underlying data structure, KnowWhereGraph integrates data from different domains and allows users to enrich their geospatial data with information about hurricanes, wildfires, debris flows, farmland types, soil types, earthquakes, and so on. This furthermore allows users to easily traverse KnowWhereGraph from within a GIS and seamlessly navigate from one domain to another. Instead of merely focusing on properties such as a fire's burn area, we are the first to link fires to place identifiers, related disasters such as landslides caused by them, and so on. Finally, because of its open-ended nature, it is rather easy to keep the graph up-to-date compared with standard, tabular GIS data. KnowWhereGraph currently provides geo-enrichment through the two most popular GIS software vendors: ArcGIS and QGIS.