A love song, a drowning, and a punchline in every verse - this is the American West laughing at its own melodrama. The forty-niners were the people who rushed to California for gold in 1849, and by 1884 their world was already a costume for comic songs like this one.
The chorus keeps one splendid antique: is the old English for "you are", surviving here (and in prayers and Shakespeare) long after everyday speech dropped it. Sing it as written - every recording does - and enjoy owning a second-person pronoun most textbooks never mention.
The whole song runs in the past simple, which makes it a painless tense drill: dwelt, was, were. Dwelt is the old past of dwell, to live somewhere - you will meet it in fairy tales and nowhere else, which is exactly the register the song is joking in. Dreadful uses dreadful as an old intensifier: dreadfully sorry, terribly sorry.
And the shoes: herring boxes - the wooden boxes fish were shipped in - "without topses", worn as sandals, in size , which is enormous. The song mourns Clementine while telling you her feet were comically large. That double game, sad tune and absurd words, is a very English-language kind of humour, and this is a fine first lesson in it.