[Abstract] The first rugby team in the U.S. was formed at Harvard University in 1872, and its first match was with Canada’s McGill University in May 1874. After that, rugby became very popular not only on the East Coast but also all over the U.S., particularly in the 1890s. However, with the rise of American football, rugby in the U.S. started to decline as early as the beginning of the 20th century, but we do not know much about what was behind this decline. This paper, therefore, focuses on the background of how rugby in the U.S. was replaced by American football. It also explains a similar situation in Japan in the late 1990s where rugby lost fans to a professional soccer league. The paper also stresses the importance of the U.S. as a future market for rugby fans in the world, though they are not necessarily familiar with U.S. rugby and its history.