Does México have a quadripoint? That’s not intended as a trick question. Ideally this should have an easily verifiable solution. Either four Mexican states touch at a common spot — a quadripoint — or they do not. The answer however is considerably more elusive. I remain at a loss as I attempt to uncover whether someone should reasonably conclude one way or the other.
There are a couple of candidates, and the Mexican states of San Luis Potosí and Zacatecas are common denominators.
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Notice the relative proximity of the states of Jalisco, Guanajuato, San Luis Potosí, and Zacatecas. A small notch of Zacatecas protrudes just far enough south to prevent Jalisco and San Luis Potosí from sharing a common border according to Google Maps, with all of the usual caveats about the accuracy of Google Maps. The situation seemingly separates the two states by about 1.88 kilometres (1.17 miles) according to my quick calculation.
This is an agricultural area farmed and ranched fairly intensively judging by satellite mode and confirmed by proximal Street View availability (sample image). There’s even a ranchero within the Zacatecas notch, which would be an interesting geo-oddity homestead for the lucky resident: a click east to San Luis Potosí; a click south to Guanajuato; a click west to Jalisco. It’s easily accessible from the nearest town, Ojuelos de Jalisco, less than 12km down a road called Deportiva (which translates to "sports" and runs by the town’s athletic fields as it departs town). A driver would also cross the border between Jalisco and Zacatecas a couple of times for good measure too (map).
This happy confluence of multiple borders didn’t seem to be controversial. It did in fact appear to represent two tripoints falling in very close proximity to each other. A cube of Zacatecas less than 2km on a side blocked a rare opportunity for a quadripoint.
The other potential Mexican quadripoint takes place in the vicinity of Coahuila, Nuevo León, San Luis Potosi and Zacatecas either where they all join together or where they all nearly do so, depending on the evidence one chooses to accept.
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Google Maps sides clearly with the camp that believes in two tripoints in close proximity to each other rather than a single quadripoint, once again considering that Google isn’t the arbiter of all things geographic. However, notice the distance between to two tripoints: 12.17 km (7.56 mi). It would hardly seem to be a question with such a sizable gap. Yet, other maps are much less clear including some published by the Mexican government. The Yahoo! Group "boundarypointpoint" which specializes in just these types of situation appeared to have reached a consensus that a quadripoint did not exist, after lengthy discussions and earlier research.
However, a monument exists at what many would call the northern of the two tripoints, the "Mojonera de los Cuatro Estados" (Marker of the Four States). There are various photographs of the marker posted on the Intertubes although none that I could find with Creative Commons licensing so I couldn’t embed them here. Feel free to open a photo from Panoramio or from Flickr in another tab and observe the results. The marker would be readily accessible albeit after enduring a jarring 8.1 km (5.0 mi) ride down a rough road. I think the guy in the Flickr image with the mountain bike had the right idea.
Wikipedia bought into the idea of a Mexican quadripoint, for what that’s worth. It was presented as fact without citing any evidence, and was immediately flagged as such. Wikipedia attempted to weasel-word around the issue by stating that this is the place where the four states "effectively" meet. Right. I’m not sure de facto or close-enough provides a decent standard for a concept that implies precision. Even the contributors on boundarypointpoint seemed conflicted after the revelation of the Mojonera de los Cuatro Estados.
Examining the Mexican Geological Service website, Servicio Geológico Mexicano, provided nothing definitive and Internet searches using the Spanish-language term "Cuadripunto" yielded no better results either.
Was it a situation created by imprecise surveying techniques like the Delaware Wedge? Is it so rural and effects so few people that the governments involved simply don’t consider it enough of a priority to figure it out? Or has it been overtaken by events with a named boundary stone, the Mojonera de los Cuatro Estados, converting a close-enough approximation to an exact declaration?
In my mind, the elusive Quadripoint of México remains a mystery.