Baltic porter was introduced from Britain in the 18th century as a top - fermenting beer and remained so when local breweries -- such as Carnegie in Sweden -- began to produce it in the early 19th century .
Baltic porter was introduced from Britain in the 18th century as a top - fermenting ( i.e. , ale - style ) beer . 
 It remained an ale when local breweries -- such as Carnegie in Sweden -- began to produce it in the early 19th century .