Scarce map of Central America, extending from southern Mexico to modern Colombia, omitting the northern Yucatan peninsula, highlighting the many conflicting boundary claims of the region. Detailed insets show the 'Isthmus of Panama' and various cross-sections of the country between Atlantic and Pacific, to illustrate the proposed routes to link Atlantic and Pacific, with a table of distances, the routes across the Isthmus of Panama and Isthmus of Darien being the shortest.

This fourth state has been revised to show the international arbitration by representatives of the British and American governments to resolve the boundary dispute between Nicaragua and Costa Rica in 1852, and the boundary of 'Grey Town or San Juan de Nicaragua', laid down in 1852.