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Notes:
The 'CENSUSTRACTS' layer contains 1990 Census tract boundaries that have been clipped by the county outline. In most cases this clipping renders a recognizable county outline, but in areas where the legal county line is offshore (San Francisco, San Mateo, Alameda, Contra Costa) the tracts will extend beyond the shoreline to the legal county line and will appear unusual. The source for this layer is the 1990 TIGER/Line files. The attribute file contains the PL94-171 data (all fields) for the census tracts, and two density items. The TIGER/Line data was re-issued several times. Early versions had corrections to the line work, some of which had to do with county boundaries. The post-census county lines do not match the Teale library's county lines.
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