Hildebrand was known for his many influential textbooks in mathematics and numerical analysis.
[1] He then received his Ph.D. degree from Massachusetts Institute of Technology in 1940 under the supervision of Prescott Durand Crout.
[1] During World War II, he worked for two years in the Radiation Laboratory.
At MIT, he taught 18.075 and 18.076, the classes on advanced calculus for engineering students.
The big green textbook from these classes (originally Advanced Calculus for Engineers, later Advanced Calculus for Applications) was a fixture in engineers' offices for decades.