The cholera outbreak which John Snow described took place on Abbey-row (shown in red), labeled in the 1862 map as "Sfift Row," across the eastern branch of the Lea River from a flour mill.  The location of the shallow pump well is shown in blue.  The pump supplied water for the residents of Abbey-row, persons living in the flour mill, and several other households near the mill by the river.  For a larger, less detailed view, as shown in an earlier 1841 map, click here.

Source: Stanford's Library Map of London and its Suburbs. Published by Edward Stanford, 6, Charing Cross, London, February 15, 1862.