History of Scottish Gaelic
All surviving dialects are Highland and/or Hebridean dialects. Dialects of Lowland Gaelic have become defunct since the demise of Galwegian Gaelic, originally spoken in Galloway, which seems to have been the last Lowland dialect and which survived into the Modern Period. By the 18th century Lowland Gaelic had been largely replaced by Lowland Scots across much of Lowland Scotland. According to a reference in "The Carrick Covenanters " by James Crichton, the last place in the Lowlands where Scottish Gaelic was still spoken was the village of Barr in Carrick: only a few miles inland to the east of Girvan, but at one time very isolated. Crichton gives neither date nor details.
Canadian Gaelic
While there have been many different regional dialects of Scottish Gaelic that have been spoken in communities across Canada, Atlantic Canada is the only area in North America where Gaelic continues to be spoken as a community language, especially in Cape Breton. All of these dialects had their origins in the Highlands and Islands of Scotland, although some have become effectively dormant since the time of emigration. Even in Cape Breton, the situation of the language is precarious.