USGS topo shades "Inholdings" and comments in legend, "Non-National Forest System lands within the National Forest; Inholdings may exist in other National or State reservations".
Forest Service topo marks "Inholdings" and comments, "Private Land within National Forest".
Wikipedia entry tells me, "An inholding is privately owned land inside the boundary of a national park, national forest, state park, or similar publicly-owned protected area. Inholdings result from private ownership of lands prior to the designation of the protected park or forest area, which then end up grandfathered within the legally designated boundary.
"In the United States, the main causes of inholdings are checkerboarding due to railroad land grants under the Pacific Railway Acts beginning in 1862, homestead claims under the 1862 Homestead Act, and mining claims patented under the General Mining Act of 1872, along with the more recent Alaska Native Claims Settlement Act of 1971. The railroad checkerboarding primarily affects national forests, while inholdings due to the other types of claims occur frequently within national parks and national forests throughout the western United States. Over the last several decades, conservation groups have lobbied the United States Congress to acquire inholdings especially within designated wilderness areas, either by direct purchase or via land exchange which trades the inholding for other federal lands located outside of national parks or wilderness areas."
