In 1913, Penck's idea came to fruition when an international conference was held to establish standards for the maps, which also became known as the Millionth Map of the World due to the map series' scale. The 1913 standards established that maps would use the local form of each place name in the Roman alphabet (thus, languages that use other alphabets would need to transliterate their place names). Map colors were standardized as well - towns, railroads, and political boundaries would be represented in black, roads would be red, and topographic features would be brown.
Each country would be responsible to create their own maps, which posed a problem for developing countries at the beginning of the twentieth century that had never performed a survey of their country nor could they afford such a survey. Each map would have a legend printed in English and French and the title of the maps would be written in French, Carte Internationale du Monde au 1 000 000.
Following the Paris conference, the "Central Bureau of the Map of the World" was established at the offices of Great Britain's Ordnance Survey. After 1913, over three dozen countries began to produce maps. However, by the start of World War I only eight maps, out of the total 2500 had been produced.
In 1921, the American Geographic Society took it upon themselves to produce the map sheets for the countries of Central and South America. They worked from 1921 to 1946 to produce 107 maps, a project that cost the organization $570,000.
By the 1930s, 405 maps had been produced although only half adhered to the standards of the project. During World War II, the International Map of the World project suffered because the Bureau offices, along with the archives and data for maps, were destroyed by bombing.
The newly-created United Nations took control of the Millionth Map project in 1953 and watched international interest slacken over the following decades. By the 1980s, only about 800 to 1000 total maps had been created (and less than half were accurate or based on the standards), and the U.N. stopped issuing their regular reports about the status of the project.
It's quite unfortunate that such a worthy and useful international project died, although it's not difficult to imagine how challenging it would be to obtaining the cooperation of every country on earth to adhere and to care about the project.