Although his PhD requirements were finished by 1912, he did not receive his actual degree until an informal oral exam in 1924, with his 1924 USGS bulletin on the Manhattan mining district in Nevada being accepted as his dissertation.

"[2] Ferguson continued to do fieldwork in Nevada after his retirement from the USGS, but in 1957 he suffered the loss of an eye when the steel head of a geologic pick shattered.

Between 1951 and 1954, Ferguson, Muller, Stanley H. Cathcart, and Ralph Roberts (in various combinations) published seven US Geological Survey 1:125,000 quadrangle maps of Nevada, including Winnemucca and Golconda.

[8] In 1941, Ralph Roberts, on one of his first assignments as a USGS employee, joined senior geologists Ferguson and Siemon Muller on a project mapping the Sonoma Range in Nevada.

[3] Roberts and Ferguson (along with Preston E. Hotz and James Gilluly) were coauthors on a 1958 paper that helped lead to the discovery of the Carlin gold deposits.

[4][13] Following the wedding, they went on a year-long honeymoon in South America, and then settled into a house in NW Washington, D.C.[11] In 1922, Alice Ferguson purchased a 139-acre (56 ha) farm named Hard Bargain in Accokeek, in southern Maryland, as a weekend retreat for her husband and herself.

When Native American artifacts were discovered on the property, Alice started archeological excavations, with the occasional assistance of Henry and his geologist colleagues, such as Thomas Nolan.

In 1957, Ferguson was one of the founders of the Accokeek Foundation, an organization dedicated to preserving the "natural beauty along the Maryland shore of the historic Potomac River.