The Chicago River once drained into Lake Michigan. In January 1900, engineers opened the Sanitary and Ship Canal and reversed the current, pushing the city's water toward the Mississippi basin instead. The route that Lake Michigan Sunset Cruise in Chicago tours follow today was fixed by that decision: a river running backwards, a lock at the harbor mouth, and a lakefront kept clear of buildings after Montgomery Ward sued the city four times between 1890 and 1911. The Great Chicago Fire of 1871 destroyed roughly 3.3 square miles of the young city and cleared ground for the architects who followed. William Le Baron Jenney's Home Insurance Building of 1885 introduced the steel skeleton frame. Daniel Burnham's 1909 Plan of Chicago turned the shoreline into public parkland and set the terraced setbacks that read clearly from the water. The result is a wall of buildings best understood from offshore, where the Wrigley Building's white terra cotta, Tribune Tower's flying buttresses, Marina City's twin corncob towers of 1964 and the 442 metres of Willis Tower sit in a single frame. Sightseeing on the water is younger than the skyline it studies. The Chicago Architecture Foundation launched its first docent-led river trips in 1983, the ancestor of today's Chicago architecture river cruise; commercial fleets followed within a decade. The Chicago Harbor Lock, completed in 1938, still separates the two bodies of water, dropping or lifting each vessel the foot or two that divides river level from lake level. Above it, the DuSable Bridge of 1920 marks the site of Fort Dearborn; below it, the Riverwalk now runs continuously from Lake Shore Drive to Lake Street. Navy Pier, opened in 1916 as Municipal Pier and rebuilt in 1995, sits at the northern edge of the same route. Chicago boat tours of the skyline carry more traffic through the lock each summer than freight does. Golden hour explains the rest. Between June and August the sun drops behind the West Loop after eight in the evening, and the west-facing glass of Aqua Tower, the Aon Center and Lake Point Tower holds the light for several minutes longer than the streets below. Offshore, the Chicago Harbor Lighthouse — built for the 1893 World's Columbian Exposition and moved to its breakwater in 1919 — marks the point where the lake opens and the skyline resolves into a single silhouette. A Lake Michigan Sunset Cruise in Chicago tour is, in that sense, a reading of 150 years of engineering from the angle its builders assumed no one would ever take.