Q. When a plural possessive ends a sentence, where does CMOS recommend that the apostrophe fall—before or after the period? For example: Because UAVs fly relatively close to the ground, their surveillance “footprints” are smaller than the satellites’. Is there a rule in CMOS that covers this?

A. Yes. Please see CMOS 6.118: “An apostrophe should not be confused with a single closing quotation mark; when a word ends in an apostrophe, no period or comma should intervene between the word and the apostrophe.”