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
By 1850, Gaelic was the third most-common mother tongue in British North America after English and French (when excluding Indigenous languages), and is believed to have been spoken by more than 200,000 British North Americans at that time. A large population who spoke the related Irish Gaelic immigrated to Scots Gaelic communities and to Irish settlements in Newfoundland.