My favorite teacher, who likes to teach “outside the box,” took our American studies class on a field trip to the Old Manse, whose most famous resident was Nathaniel Hawthorne.

My favorite teacher, who likes to teach “outside the box,” took our American studies class on a field trip to the Old Manse whose most famous resident was Nathaniel Hawthorne.

In the first sentence, the two subordinate clauses (who likes…and whose most famous…) are nonrestrictive (nonessential) and are correctly set off with commas.