Originally Posted by
YVR Cockroach
Duty-free purchases in the U.S. are brought to the gate and picked up by pax at the jetway as they board so the answer is no, you cannot buy and put it in your checked bags.
Certainly not on the first leg, but presumably the OP will claim their luggage, clear customs in YOW and re-check their bag for the 2nd leg to YVR, in which case they can put the bottle in their checked bag for the second leg.
That being said, I agree with cockroach - If I'm in the USA and checking a bag I usually just buy my booze at a liquor store and pack it. It's usually the same price as duty free, with greater selection and less hassle.