NOAA Nautical Chart "DRY TORTUGAS" 1:30000 from 1997 on page http://historicals.ncd.noaa.gov/historicals/histmap.asp archive copy at the Wayback Machine downloadable as *.sid file (a wavelet format viewable by "GeoExpress View by ILS"), converted to jpg (because sadly Wikipedia does not accept this great graphic format) and reduced resolution by half

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