The daughter of a U.S. senator from Idaho, Mary Brooks served as an Idaho state senator from 1963 to 1969. She served as the Director of the U.S. Mint from 1969 to 1977, and when she was appointed by President Nixon she became the third woman in history named to the post. She oversaw the production of the Eisenhower dollar coin, as well as the design of the Bicentennial quarter, half dollar, and dollar coins for the United States Bicentennial. She is credited with saving the original San Francisco Mint building, known as the "Granite Lady," by transferring it to the Treasury Department. Brooks was awarded the "I Left My Heart in San Francisco" Award in 1974 for her preservation efforts.

In addition to her political appointments, Brooks took over her father's sheep ranch after his death in 1945 and ran it until her son took it over in 1961. Her son, John Peavey, served over twenty years in the Idaho senate. Mary graduated from Gooding High School in 1925, attended Mills College in Oakland, California. She transferred to the University of Idaho in 1927, where she was a member of the Kappa Kappa Gamma sorority and received her bachelor's degree in economics in 1929.

During her tenure as Director of the Mint, Mary famously led a tour of the U.S. Bullion Depository at Fort Knox, Kentucky for members of Congress and the news media on September 23, 1974. Additionally, she was awarded the American Numismatic Association's Medal of Merit in 1988, and was the first woman to recieve the United States Treasury Department's highest honor, the Alexander Hamilton Award. She was inducted into the University of Idaho Alumni Association's Hall of Fame in 1970.