Side-channels are a typical element of earth or rockfill dams to discharge floods sideways instead frontally, such as normally adopted for concrete dams. The side channel received attention from the hydraulics community from the 1920s, once the first large mentioned dams were erected, and its use culminated at Hoover Dam in the mid 1930s, based on a large test program. This paper highlights the major advancement of this basic element of hydraulic structures up to the late 1950s,both describing key installations over the world, and the actors who have furnished the governing design equations for water flow with spatially-increasing discharge. Short summaries on the biographical background are also provided, along with a discussion of the main literature that allowed for the current knowledge in this fascinating field of open channel flow.