This posting sets out the where one can obtain geologic maps of Lanark County and adjoining parts of Eastern Ontario. It concentrates on online sources for the maps.
Ontario Geological Survey
The best source for geologic maps issued by Ontario Geological Survey is the web page listing OGS Publication Types, which can be found at:
http://www.geologyontario.mndmf.gov.on.ca/gosportal/GeologyOntarioFAST/pubs/pub_index.html 
Maps and publications are free to download from this site. The maps and publications are indexed under a Series Code. The Following "P" series maps are useful:
P2723 - Paleozoic geology, Westport area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2723/P273.pdf
P2724 - Paleozoic geology, Perth area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2724/P2724.pdf
P2725 - Paleozoic geology, Carleton Place area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2725/P2725.pdf
P2726 - Paleozoic geology, Arnprior-Quyon area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2726/P2726.pdf
P2493 - Paleozoic geology of the Kemptville area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2493/P2493.pdf
P2494 - Paleozoic geology of the Merrickville area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2494/P2494.pdf
P2495 - Paleozoic geology of the Brockville-Mallorytown area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2495/P2495.pdf
P2496 - Paleozoic geology of the Gananoque-Wolfe Island area, southern Ontario 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2496/P2496.pdf 
P 2611 - Geology and Mineral Deposits of the Kingston area, southern Ontario; 1985 , scale 1:250 000.
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2611/P2611.pdf
P2621 - Sand and gravel assessment, Lanark County, north half 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2621/P2621.pdf
P2622 - Sand and gravel assessment, Lanark County, south half 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2622/P2622.pdf
Anyone that wants a paper copy of one of those maps can obtain the map from Ontario’s Ministry of Northern Development and Mines. The cost last year was $2 per map plus $5 for shipping. Their contact information is:
MNDM Publication Sales
933 Ramsey Lake Rd., Level A-3
Sudbury, Ontario P3E 6B5
Local: (705) 670-5691 
Toll-Free: 1-888-415-9845, ext. 5691 (inside Canada, United States)
Fax: 705-670-5770 
Pubsales.ndm@ontario.ca
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Other maps of interest that can be obtained from the Ontario Geological Survey are M1 1900 series , M2 2000 series and M5 5000 series maps:
M1956-04 - Clarendon-Dalhousie-Darling area, counties of Frontenac and Lanark 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M1956-04/M1956-04.pdf
M2515 - Precambrian geology, Lavant area, Frontenac and Lanark counties 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M2515/M2515.pdf
M2544 - Bedrock geology of Ontario, southern sheet 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M2544/M2544.pdf
M2545 - Bedrock geology of Ontario, explanatory notes and legend 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M2545/M2545.pdf
M2556 - Quaternary geology of Ontario, southern sheet 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M2556/M2556.pdf 
M5511 - Renfrew, NTS 31F/SE, data base map, southern Ontario engineering geology terrain study 
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/M5511/M5511.pdf 
M5512 - Renfrew, NTS 31F/SE, engineering capability map, southern Ontario engineering geology terrain study 
M5513 - Ottawa, NTS 31G/SW and part of NTS 31G/NW, data base map, southern Ontario engineering geology terrain study 
M5514 - Vankleek Hill, NTS 31G/SE and part of NTS 31G/NE, data base map, southern Ontario engineering geology terrain study 
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Geological Survey of Canada
The best online source for publications and maps issued by the Geological Survey of Canada is  the GEOSCAN: Publications database, which can be found at:
http://geoscan.ess.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/geoscan_e.web
The following maps are useful. Googling the digital object identifier (e.g., doi:10.4095/107951), including "doi:", will take one directly to the download site for the map.
Geology Perth, Lanark and Leeds Counties, Ontario 
Wilson, M E; Dugas, J; Geological Survey of Canada, "A" Series Map 1089A, 1961; 1 sheet;   doi:10.4095/107951
Renfrew, Renfrew and Lanark Counties, Ontario 
Quinn, H A; Geological Survey of Canada, "A" Series Map 1046A, 1956; 1 sheet, doi:10.4095/107619
Nepean, Carleton, Lanark, Grenville, Dundas, Gatineau and Papineau Counties, Ontario and Qu
ébec 
Wilson, A E; Geological Survey of Canada, "A" Series Map 588A, 1940; 1 sheet, doi:10.4095/107428
Province of Ontario, parts of counties of Renfrew, Lanark, Lennox, Addington, Frontenac and Carleton (Perth sheet no 119) 
Ells, R W; Geological Survey of Canada, Multicoloured Geological Map no. 789, 1904; 1 sheet, doi:10.4095/107516
Map showing the occurrences of iron ores and other minerals in portions of the counties of Frontenac, Lanark, Renfrew and Leeds, Ontario 
Ells, R W; White, J; Geological Survey of Canada, Multicoloured Geological Map 626, 1900; 1 sheet, doi:10.4095/108087
Map of Lanark County and parts of Renfrew and Leeds, Ontario 
Geological Survey of Canada; Geological Survey of Canada, Multicoloured Geological Map 103, 1875; 1 sheet, doi:10.4095/214374
 
Surficial Geology, Perth, Ontario 
Kettles, I M; Geological Survey of Canada, "A" Series Map 1800A, 1992; 1 sheet, doi:10.4095/183815
Geology Westport, Ontario 
Wynne-Edwards, H R; Geological Survey of Canada, "A" Series Map 1182A, 1967; 1 sheet; 1 CD-ROM, doi:10.4095/108032
Geology, Tichborne, Ontario 
Wynne-edwards, H R; Geological Survey of Canada, Preliminary Map 33-1964, 1965; 1 sheet, doi:10.4095/108606
Geology, Brockville-Mallorytown area, Ontario 
Wynne-Edwards, H R; Geological Survey of Canada, Preliminary Map 7-1963, 1963; 1 sheet; , doi:10.4095/108670
Geology, Gananoque, Ontario 
Wynne-Edwards, H R; Geological Survey of Canada, Preliminary Map 27-1962, 1962; 1 sheet; doi:10.4095/108828
Geological map of eastern Ontario, western Quebec, and northern New York State,
 by Sanford, B V; Arnott, R W C;  Figure 3  in Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec, and northern New York State; Sanford, B V; Arnot, R W C; Geological Survey of Canada, Bulletin no. 597, 2009; 1 sheet; doi:10.4095/247673
Geology, Carleton Place, Ontario 
Reinhardt, E W; Wilson, A E; Liberty, B A; Geological Survey of Canada, "A" Series Map 1362A, 1973; 1 sheet, doi:10.4095/109147
Ottawa, Carleton, Gatineau, and Papineau Counties, Ontario and Qu
ébec 
Wilson, A E; Geological Survey of Canada, "A" Series Map 1038A, 1954; 1 sheet, doi:10.4095/107547
Ottawa-Cornwall, Ontario and Qu
ébec 
Wilson, A E; Geological Survey of Canada, "A" Series Map 710A, 1942; 1 sheet, doi:10.4095/107616
Prescott, Ontario 
Wilson, A E; Geological Survey of Canada, "A" Series Map 852A, 1946; 1 sheet, doi:10.4095/107544
Ottawa Sheet, East Half, Carleton and Hull Counties, Ontario and Quebec 
Wilson, A E; Geological Survey of Canada, "A" Series Map 413A, 1938; 1 sheet, doi:10.4095/107511
Ottawa Sheet, West Half, Carleton and Hull Counties, Ontario and Quebec 
Wilson, A E; Geological Survey of Canada, "A" Series Map 414A, 1938; 1 sheet, doi:10.4095/107545
 
Christopher P. Brett
Perth, Ontario