Illig married Stirling on December 11, 1933. For their honeymoon, she accompanied Stirling as he traveled around the Southeastern United States conducting archaeological excavations for the Public Works Administration. During this time she trained in field archaeology alongside a number of young scholars who would go onto become prominent figures, including Gordon Willey, James A. Ford, Jesse D. Jennings, and Marshall T. Newman. In 1938, the Stirlings visited Mexico for the first time. While Marion, pregnant with her first child, visited Mitla and Monte Albán, Matthew traveled eight hours on horseback from Tlacotalpan to Tres Zapotes, to see the Olmec colossal head discovered there by José María Melgar y Serrano in 1862. He found that the sculpture was surrounded by a substantial archaeological site and, upon returning to the United States, the Stirlings obtained grants from the National Geographic Society and Smithsonian Institution to explore the area further. Between 1939 and 1946, they conducted eight expeditions to Southern Mexico, which according to National Geographic "essentially rewrote Mesoamerican history". Pugh's role on the excavation was as "housekeeper, bookkeeper, and supervisor of artifact preparation in the field laboratory". Stirling described her as his "co-explorer, co-author and general co-ordinator". Pugh was a member of the Association of American Geographers and served as the president of the Society of Woman Geographers twice, in 1960–1963 and 1969–1972. She won the National Geographic Society's Franklin L. Burr Award in 1941, along with Matthew Stirling and Richard Hewitt Stewart, and the Society of Women Geographers' Gold Medal in 1975. She had a long association with the Textile Museum at George Washington Museum, serving as a trustee, secretary, treasurer, vice president and president, and establishing a fund for the acquisition of Latin American textiles.
Pugh's first husband Matthew Stirling died in 1975. They had two children, Matthew W. Stirling Jr. and Ariana Stirling Withers. She was married to John Ramsey Pugh, a retired general involved with the Textile Museum, from 1977 until his death in 1994. She died in Tucson, Arizona, on April 24, 2001. While in her 80s, she travelled to Antarctica. The Stirling archives were donated by their grandchildren to the National Anthropological Archives at the Smithsonian Institution in 2006.
Selected publications
Stirling, Matthew and Marion I. Stirling. "Tarqui, an early site in Manabi Province, Ecuador." Bureau of American Ethnology, Anthropological Paper 63, Bulletin 196 : 1–28.
Stirling, Matthew and Marion I. Stirling. "Archaeological notes on Almirante Bay, Bocas del Toro, Panama." Bureau of American Ethnology, Anthropological Paper 72, Bulletin 191 : 255–284.
Stirling, Matthew and Marion I. Stirling. "The archeology of Taboga, Uraba and Taboguila Islands, Panama." Bureau of American Ethnology, Anthropological Paper 73, Bulletin 191 : 285–348.
Stirling, Matthew and Marion I. Stirling. "El Limon, an early tomb site in Cocle Province, Panama." Bureau of American Ethnology, Anthropological Paper 71, Bulletin 191 : 247–254.