Yeah, the old way is to prime it with sugar and seal it to create the carbonation after the fermentation cycle. Home brewers do this to carbonate in bottles. I don't know how this would have been done back in the 1800s. Bottled beer would be expensive to transport vs barrels, but do barrels go flat after they're tapped?

There's a lot of variables that if there was a process it would be interesting. At the same time it would make more sense to just serve wine and liquor.