He served in the United States Navy during World War I and later attended the University of California, Berkeley where he received an M.A.
Hildegarde's sister was Janet Flanner, a long time Paris correspondent for The New Yorker, (writing under the pen name Genet).
Monhoff served as a design architect for the Los Angeles County Architectural Divisions and designed numerous public buildings and private residences in Southern California in the Los Angeles area, Malibu, Santa Barbara, Palm Springs, Orange County, and in Northern California in the Napa Valley.
In early 2000, Monhoff's work was featured in the Sweet Briar College gallery exhibition, White to Blue: American Art as Reflection of Social Class in the 20th Century.
Collections of Monhoff's archived papers, architectural plans, and art work are held at University of California, Los Angeles (UCLA), the De Young Museum in San Francisco and the Smithsonian American Art Museum in Washington, D.C.