The Katahdin Woods and Waters National Monument Seboeis Unit Vegetation Mapping Project was initiated in the fall of 2019 by a grant through the USGS Natural Resource Preservation Program to classify and map vegetation types of the Seboeis Unit thereby providing resource managers and biological researchers with useful baseline vegetation information. This layer provides the vegetation map for the Seboeis Unit. Information for this layer was collected in 2019 and 2020. After completion of the accuracy assessment process, 33 map classes represent the Seboeis Unit of the monument. Of the 33 map classes that represent the Seboeis Unit, 28 represent natural (including ruderal) vegetation types, consisting of 50 U.S. National Vegetation Classification (USNVC) association types. For the remaining 5 of the overall 33 map classes, 2 represent USNVC cultural types for barren areas and developed areas and 3 represent non-USNVC types for non-vegetated open water. Of the 28 map classes representing natural (including ruderal) vegetation types, 15 represent a single vegetation type (when it exists above an the minimum mapping unit [MMU]), 7 represent 2 vegetation types mapped together, 5 represent 3 vegetation types mapped together, and 1 represents 6 vegetation types mapped together. Polygon units were mapped to either a 0.5 ha or 0.25 ha minimum mapping unit, depending on vegetation type. Collectively, the spatial-database layer (vegetation map) produced for the Seboeis Unit vegetation mapping project consists of 1,261 polygons and covers 4,854.8 ha, with an average polygon size of 3.8 ha. The 28 map classes representing natural (including ruderal) vegetation types apply to 97.6% of polygons (1,231 polygons; average size of 3.9 ha) and cover 98.6% of the Seboeis Unit (4,787.5 ha). Further broken down, map classes representing natural vegetation types indicate that the Seboeis Unit is 93.2% forest and woodland (4,526.6 ha), 4.0% shrubland (195.3 ha), and 1.3% herbaceous cover (65.6 ha). Map classes representing cultural vegetation types in the USNVC apply to 1.0% of polygons (12 polygons; average size of 2.5 ha) and cover 0.6% of the Seboeis Unit (29.7 ha). Map classes representing non-vegetation open and flowing water (non-USNVC) apply to 1.4% of polygons (18 polygons; average size of 2.1 ha) and cover 0.8% of the Seboeis Unit (37.4 ha). The information in this layer is explained in depth in the report titled Vegetation Map for the Seboeis Unit of Katahdin Woods and Waters National Monument.