Fòram na Gàidhlig

I found out today that Baltimore (the city is named after Lord Baltimore) is apparently the English version of the Irish Baile an Tí Mhóir, or Town of the big house.

So, would the Gaelic equivalent be Baile an Taigh Mòr, or would the fact that it's the town of the big house bring the genitive to bear, perhaps Baile Taighe Mòr?

It would be Baile an Taighe Mhòir. Gaelic has two types of lenition, single and jumping. For example, aon causes lenition just the once:
aon chù mòr
aon bhalach beag

But feminine nouns, the definite article and slenderisation in masculine nouns cause jumping lenition, i.e. it keeps going until the phrase ends:
air an taigh mhòr bhlàth bhuidhe
doras an taighe mhòir bhlàith bhuidhe
clach mhòr bhlàth bhuidhe

Make sense?

That does make sense to me, yes.

Ceud taing!