Lanark is an unincorporated community and former village in the municipality of Lanark Highlands, Lanark County, in Eastern Ontario, Canada. It was a separate village municipality from 1862 until May 14, 1997, when it merged with Lavant Dalhousie and North Sherbrooke Township and Lanark Township to form the Township of North West …Lanark is an unincorporated community and former village in the municipality of Lanark Highlands, Lanark County, in Eastern Ontario, Canada. It was a separate village municipality from 1862 until May 14, 1997, when it merged with Lavant Dalhousie and North Sherbrooke Township and Lanark Township to form the Township of North West Lanark.