In 1937 Hoppé visited the African countries of Rwanda, Uganda, Nigeria, Kenya, Cameroon, Ghana, Tanzania, and the Democratic Republic of the Congo. His documentation in these diverse regions was focused primarily on the daily lives of the native people, their ceremonies and routines, and secondarily on their interaction of the outside world. Hoppé photographed dancing ceremonies, hunting and initiation rituals, landscapes and market scenes, as well as aspects of developing foreign interaction in port cities and government compounds. Hoppé's work exemplifies the mixing of the ancient third world with the modern, developing first world.

In the autumn of 1929 Hoppé spent several months touring the Indian Subcontinent to document the diverse geography and material cultures of these countries. Hoppé’s appearance in khakis and a plinth helmet clearly marked him as an outsider but his skill photographing, especially in the highly populated cities, was more than simply a technical achievement. Using mostly small, hand-held cameras, his photographs show unusual sensitivity and insight into the peoples and a spontaneity and distinctly modern approach heretofore absent from most photographs of India. With great sympathy to nuances of these Asian cultures, Hoppé presents the social, cultural and religious fabric of regions that had been unchanged for centuries. He also records the effects of British colonization, providing us with a range of subjects spanning the wide range of India’s social ladder.

Hoppé had made regular visits to New York since 1919 and by 1921 he had established a studio on New York's West 57th Street. He mixed with and photographed America’s intellectual and artistic elite including such eminent figures as Albert Einstein, Paul Robeson, N.C. Wyeth, James Montgomery Flagg, Paul Manship, Robert Frost, Anita Loos, Eugene O’Neill, Carl Sandburg, and an aging Oliver Wendell Holmes. In between his portrait sittings he ventured out of the studio to make Cubist inspired views of the city showing it's brave new architecture. Continuing his work on human typology he made street portraits including down-and-outs in New York's Bowery district that can be compared to contemporaneous works by American photographer, Paul Strand. Beginning in late 1925 and throughout most of 1926 Hoppé traveled throughout the United States making photographs for his book Romantic America for German publisher Ernst Wasmuth. Like Walker Evans, who photographed the Eastern and the Southern states of America a decade later, Hoppé looked across the entire country through a similar Modernist lens making well over 2,100 large-format negatives.

In the early 20th century, E.O. Hoppé began one of the most unique photographic documents of London where for over forty years he worked tirelessly to record London’s transition from a 19th century city into a modern metropolis. Systematically chronicling the landmarks and architectural fabric that defined the city of London, Hoppé’s work can be compared both in scale and modernistic approach to Eugene Atget’s photographs of Paris and Bernice Abbott’s of New York.