The Chicago River runs backwards. Engineers reversed the flow in 1900, pulling the current away from Lake Michigan and into the Sanitary and Ship Canal to carry sewage downstate. What began as a public-health measure produced a navigable corridor through the center of a skyscraper city, and the passenger fleet that works it today owes everything to that decision. Chicago Cruise Fireworks sailings are the most recent chapter in a long negotiation between the city and its water. Thirty-eight movable bridges cross the river system, most of them double-leaf bascule spans counterweighted below the sidewalk. The DuSable Bridge at Michigan Avenue opened in 1920 and still carries four bridgehouse pylons at its corners. Downstream the Wrigley Building's glazed terra cotta reads cream under floodlight. Across the water, Tribune Tower holds stone fragments taken from the Parthenon and Notre-Dame, set into its limestone base at eye level. Marina City's twin towers, completed in 1964, drop sixty stories straight into their own boat slips. These are the Chicago River landmarks that a deck delivers in sequence rather than one at a time. Navy Pier has launched fireworks over the lakefront for three decades, and the display remains one of the few civic spectacles better read from the water than the curb. Vessels bound for the lake pass through the Chicago Harbor Lock, a chamber that steps them down from river level and out past the breakwater. Those staying inside the gates watch the shells reflected in glass curtain walls on both banks. Chicago Cruise Fireworks tours divide along exactly that seam — lake viewing or river viewing — and the same hulls run both. The Chicago Riverwalk, extended west to Lake Street in 2016, put thousands of pedestrians at the waterline and changed how the skyline is read from below. Daytime Chicago architecture river cruise routes built that audience first, tracing Willis Tower, 150 North Riverside and the Merchandise Mart for ninety minutes at a stretch. Evening sailings inherited the fleet and the vocabulary. A Chicago Cruise Fireworks tour trades narration for altitude of a different kind: a moving hull, a shifting bearing on the Loop, and every detonation doubled on black water. The river, reversed once for sanitation, now works hardest after dark.