It’s preloaded with 100K US Topo and you add On X chips that show landowners and whatnot.
From Garmin:
Oregon 600t comes with built-in US topographic data for the entire US, including Alaska, Hawaii and Puerto Rico, and a worldwide basemap with shaded relief — all the tools for serious climbing or hiking. Map detail includes national, state and local parks and forests, along with terrain contours, elevation information, trails, rivers, lakes and points of interest.