Quote Originally Posted by Throbert McGee View Post
What if there's an explicit noun in the first clause? Like, "Вы первые американцы, ____ посетили наш город." Wouldn't a form of который be preferred to кто in that context?
Suobig made me think about the structure, and Suobig was right, you see if you use кто it requires a singular. So with посетилИ (plural) , кто can't be used.

Вы первые американцы, которые посетили наш город is correct, but alternatively one can say using the singular Вы первые американцы, кто посетил наш город (but this sounds a little bit awkward to me, though grammatically correct). I would use a participle here most likely: Вы первые американцы, посетившие наш город.