The Mercator projection was developed in 1569 by Gerardus Mercator as a navigation tool. Like the Peters map, the grid is rectangular and lines of latitude and longitude are all parallel. The Mercator map was designed as an aid to navigators since straight lines on the Mercator projection are loxodromes or rhumb lines — representing lines of constant compass bearing — perfect for ‘true’ direction. If a navigator wishes to sail from Spain to the West Indies, all they have to do is draw a line between the two points and the navigator knows which compass direction to continually sail to reach their destination. The Mercator map has always been a poor projection for a world map yet due to its rectangular grid and shape, geographically illiterate publishers found it useful for wall maps, atlas maps, and maps in books and newspapers published by non-geographers. It became the standard map projection in the mental map of most westerners. The argument against the Mercator projection by the pro-Peters folks usually discusses its ‘advantage for colonial powers’ by making Europe look a lot larger than it actually is on the globe. As far back as 1902, a cartographer warned, ‘People’s ideas of geography are not founded on actual facts but on Mercator’s map.’ (Monmonier, 21) In 1947, a U.S. State Department geographer wrote in Scientific Monthly that the ‘use of the Mercator projection for world maps should be abjured [renounced] by authors and publishers for all purposes.’ Robinson further reiterated this position in his first edition of his Elements of Cartography textbook, issued in 1953, when he called the Mercator projection ‘of little use for purposes other than navigation.’ The Mercator map is still used for navigation but that’s all it should be used for. Fortunately, over the past few decades, the Mercator projection has fallen into disuse from many reliable sources. In a 1980s study, two British geographers discovered that the Mercator map did not exist among dozens of atlases examined. Mark Monmonier also discovered that good atlases lacked the Mercator projection but that some schools still hung onto old Mercator wall maps. Unfortunately, major map companies still produce wall maps using the Mercator projection. This still needs to be corrected – while it’s impossible to purchase a Mercator wall map from school wall map publisher Nystrom, huge map companies Rand McNally, Hammond and American Map Company all still produce Mercator wall maps. In 1989, seven North American professional geographic organizations (including the American Cartographic Association, National Council for Geographic Education, Association of American Geographers, and the National Geographic Society) adopted a resolution that called for a ban on all rectangular coordinate maps. WHEREAS, flat world maps are more useful than globe maps, but flattening the globe surface necessarily greatly changes the appearance of Earth’s features and coordinate systems, and WHEREAS, world maps have a powerful and lasting effect on peoples’ impressions of the shapes and sizes of lands and seas, their arrangement, and the nature of the coordinate system, and THEREFORE, we strongly urge book and map publishers, the media and government agencies to cease using rectangular world maps for general purposes or artistic displays. Such maps promote serious, erroneous conceptions by severely distorting large sections of the world, by showing the round Earth as having straight edges and sharp corners, by representing most distances and direct routes incorrectly, and by portraying the circular coordinate system as a squared grid. The most widely displayed rectangular world map is the Mercator (in fact a navigational diagram devised for nautical charts), but other rectangular world maps proposed as replacements for the Mercator also display a greatly distorted image of the spherical Earth. Source.