This is the area most modern researchers favor for the "narrow neck of land" described in the Book of Mormon.  In its favor, it is surrounded by ancient ruins of the classical Maya and Olmec eras, as well as indiginous peoples which could relate to Book of Mormon culture.   The land below the isthmus (east and south) is largely surrounded by water and could loosely be considered an island (Alma 22:32 and 2 Ne. 10:20-21).  It is at a lower elevation than the land on either side (Morm. 4:1, 19)  However there are a number of things which mitigate against it.


1.  It is much too wide.  It is 130 miles across and would not be considered narrow by the average person.  It could not be crossed in 1 1/2 days by the average person, but would take 7 days at 20 miles per day.  Alma 22:32 and Hel. 4:7.  During the California gold rush of 1849 those who did not cross continental North America to get to the gold fields used three other routes: 1) sailing around the tip of South America and thence up to California, 2) Crossing the Isthmus of Panama, and 3) Crossing the Isthmus of Tehuantepec.  The Panama route was the preferred one, the South American route the second, and the Isthmus of Tehuantepec least preferred because it was the most difficult and dangerous. To get some idea of the width of the Istmus of Tehuantepec let us make some comparisons. It is wider than the state of Florida. It is almost as wide as the narrowest part of California. It's width is about the same as the distance from Salt Lake City, Utah to Vernal, Utah, or to Fillmore, Utah. Would you consider these distances to be "narrow"? Some researchers have suggested that Tehuantepec was narrower in Book of Mormon times, and thus could more easily qualify as the narrow neck. However archeological research has shown that ancient sites along the Gulf coast date back to the Nephite era, so that argument cannot be correct otherwise they would have been underwater. Others have suggested that the "narrow neck" is actually a narrow strip of land along the Pacific coast of Tehuantepec; however, this ignores the criteria set forth in the Book of Mormon.


2.  It is oriented in the wrong direction.  It is oriented in an east-west direction rather than the "northward" direction described in the Book of Mormon.  Alma 22:32.


3.  It is not bordered by a west sea and an east sea, but by a north sea and a south sea.  Alma 22:32.


4.  It does not have a recognizable feature called the "narrow pass".  Alma 50:34 and 52:9.


5.  It is not located at a place where the "sea divides the land".  Ether 10:20.


6.  It is unlikely that it could be completely blocked by an infestation of snakes as described in Ether 9:31-34.


7.  This isthmus would be difficult to completely fortify against an invading army.  Alma 52:9.


8.  Assuming that the Olmec and Early Formative people of this area were equivalent to the Jaredites, there are many of their ruins on both sides of this isthmus.  However the Jaredites did not build cities south of the narrow neck and preserved the land as a wilderness (Ether 10:21).  This being the case, the area of Chiapas, Guatemala, etc. could not be the land of Zarahemla.