A specialist in economic history, he studied developmentalism, international trade, and the creation of the steel and petroleum industries.
[2] Wirth's included examinations of Inca and Aztec states, urban growth in Manchester and São Paulo, and Pan-American environmental politics.
[3] Wirth, who had retired from Stanford prior to his death, had most recently turned his attention to the complex relationships between Canada, the United States and Mexico.
His last book, published by the University of New Mexico Press, tells the story of the Los Alamos Ranch School, which was displaced during World War II during the development of the Manhattan Project.
He died on June 20, 2002, in Toronto, Ontario, Canada, from a heart aneurysm while delivering a lecture to the Friends of Fort Polk, a Canadian historical society.