The assumption is understandable; the fountain sits opposite St James's Church, and the association feels tidy. But the geometry does not hold. The fountain stands roughly 320 metres west of the medieval St James's Gate, whereas documentary evidence places the well no more than about 14 metres from that gate, just outside it to the north.

The well is first described in any detail in 1610, when the writer Barnaby Rich gave an account of the annual fair held at it on the 25th of July, the feast day of St James the Apostle. Rich was not especially reverent about the occasion. He noted that the only commodity on offer was ale, that no other merchandise could be had for any money, and that attendees would first perform ritual ablutions at the well, casting the water backwards and forwards, to the right and left, and over their heads, before drinking from it and proceeding into the fair to spend the rest of the day drinking themselves insensible in what he called brothel-booths. A decade later, the Dublin Assembly Rolls of 1620 recorded a lease granted to James Veldon, a tanner, for a plot of ground immediately outside St James's Gate. The lease describes the plot's dimensions with some precision, placing the well at the northern boundary, approximately 13.7 metres from the gate itself. This document is the clearest locational evidence that survives. In 1757, the physician Dr Rutty tested water from a well he identified as St James's, which he placed in Watling Street. The well also appears on the Friends of Medieval Dublin Map of 1978, and a fountain is marked at the same general location on the 1886 Ordnance Survey sheet for the city, consistent with the 1620 lease description.

For anyone trying to trace this on foot, the area around the original St James's Gate, long since demolished, lies considerably east of the surviving obelisk fountain. The gate itself gave its name to the famous brewery established nearby, so the general neighbourhood is not hard to orientate oneself within. The 1886 Ordnance Survey sheet and Rocque's 1756 map of Dublin both repay careful study for anyone wanting to reconcile the various locations suggested by different sources. The well would have served as one of the water conduits supplying medieval Dublin, which gives it a significance beyond its religious function, though the two were never entirely separate in the life of the city.