These photos show Lock & Dam #21, just south of the city of Quincy, Illinois, on an unusually warm foggy winter day just prior to a major snowstorm. The main dam structure crosses about half the width of the river, with an earth embankment crossing the remaining 1,875 feet.

These photos show a tow of barges being locked through southbound. Like most of the Mississippi River locks, the 600 foot long lock is too short to accommodate modern tows, so the barge tow has to be broken into two sections. The upper photo shows the front group of barges tied up to the lock wall, while the third photo shows the rear group of barges being lowered in the lock. Once the lock has drained, the tow will exit, and the two sections will be joined up again for the trip to Lock & Dam #20.