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This data is found in McKeldin Library and is on CD. You will ask for a CD by call number at the McKeldin Information Desk, then you can use the GIS workstations in the 4th floor computer lab for access. Some CDs of possible interest:
DCHD technology toolbox data: historic sites layers F 182 .M33 2000 Contains layers for historic and archaeological sites and easements.
3-D Topo Quads: New Jersey, Maryland & Delaware G 1255 .D42 1999
Scanned Images of USGS 7.5' topographic quadrangles: Montgomery and Prince George's Counties G 3843 .M6 1998
From these sites, you can look at data and create maps, but you cannot download or manipulate the data.