Lower Fore street extends south along the River Thames from Church Street to Broad Street, just below the Lambeth Palace (see road in blue).  The Lambeth Bridge is seen at the top left, built in 1862 and thus not present during the life of John Snow. 

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