Way back in elementary school I remember the teacher (I think this was 4th or 5th grade) telling us that Maine was the northernmost state of the lower 48. I immediately disagreed, knowing well that this as Minnesota (thanks to the northwest angle), and that all the states of the 49th parallel with Canada extend farther north than Maine. She again disagreed, then proceeded to get a yardstick to show us on the wall map that it was indeed farther north. The map was not a Mercator where this would have been shown correctly.... I don't recall exactly but I think it was some type of Lambert Projection. I look in disbelief and muttered "you're not measuring it right"... and she kind of went "doh!" and then moved on without explaining about parallels or projections to the class.
But the myth persists. There are still people today who hold this misconception about Maine (which does hold the distinction of having the easternmost point in the United States, at the ironically named West Quoddy Head (it is west of Quoddy Strait between Maine and New Brunswick).
At any rate geography myths are everywhere, even to the point where some towns erroneously claim designations. Some are matters of semantics (i.e., various towns in the Tierra del Fuego region claim to be the world's southernmost town, but it depends on your definition of "town"). Others are just commonly perpetuated myths.
World's Shortest River?
Some friends in Texas told me of a Comal River near New Braunfels which locals proclaim to be the "shortest river in the world". It is around 3 miles long. This is nowhere close, a short investigation revealed a "D" River in Oregon which was measured at 440 feet. It flows out of a coastal lake into the Pacific. They advertised it as such and even put up signs proclaiming it as such. Then a Roe River in Montana was found that flowed some 200 feet from a spring into the Missouri River. Oregon countered by measuring their river at extreme high tide, which they claimed shortened the "D" River to 120 feet. And so on. At some point you have to argue what is a river... (and whether or not starting from a lake which has headstreams counts).
Coiba
Living in Panama I was long aware of its largest island, Coiba. Located in the Pacific off the Azuero peninsula, it was home of a feared prison colony under Noriega but otherwise undisturbed and is now a national park, where one can see Scarlet Macaws and other animals now rare on the mainland. At 503 square kilometers it is easily Panama's largest island... but locals claimed it held a greater distinction: that it was the largest island on the pacific coast of the Americas. As soon as I heard this I immediately knew it to be false... there are plenty of islands far larger on the pacific coasts of Canada (e.g., Vancouver at 31285 sq km) and Chile (e.g. Chiloé at 8394 sq km). But there is a long ways between these, so maybe it held the distinciton of largest between them.
South of Pugest Sound (which has Whidby and the Juan de Fuca islands) there aren't that many notable islands on the Pacific coast of the United States. There are a few notable small ones in San Fransisco Bay (e.g., Alcatraz)... but really the only serious archipelago is the Channel Islands of California. The largest of these is Santa Cruz, which is just under 250 sq km, which makes it about half the size of Coiba.
Moving south into Mexico there are a number of decent-sized islands, the largest being in the Gulf of California, one called Ángel de la Guarda and another called Tiburón. The former is sq 931 km and the latter is 1201 sq km. Both far larger than Coiba. So already we need to curtail the claim to "south of the Gulf of California".
Continuing on there is nothing to threaten it through the rest of Central America or Columbia until we get to Ecuador. Ecuador has the Galapagos Islands which are a fair distance from the coast. The largest island of the chain is Isla Isabela, at 4640 sq km, easily larger than Coiba. But even if you don't venture off the coast, there is Isla Puná, at 865 sq km, located in the Gulf of Guayaquil.
So the proper claim is that Coiba is the largest island on the pacific side of the Americas betwen the Gulf of California and the Gulf of Guayaquil. Or to make it simpler, just call it the largest Central American Island in the Pacific. Or just the largest Central American Island (the largest on the Carribean Coast I can find is Roatan, at around 90 sq km)... though Cozumel in the Yucatan is larger, but Mexico is not normally considered part of Central America.
