Q. When did Chicago Manual of Style first state that ending a sentence with a preposition is not wrong (section 5.180 in current CMOS)?

A. CMOS has never prohibited a preposition at the end of a sentence in any of its versions and editions since 1906. The first edition to state positively that a preposition may end a sentence was the 15th, in 2003, the first edition of the Manual to contain a chapter on grammar.