[1][a] The Bonsals descended from English Quakers who participated in founding the colony of Pennsylvania in 1682.

Born in Bedford, New York, Bonsal received an Artium Baccalaureus degree from Dartmouth College in 1927 and a Bachelor of Laws from Harvard Law School in 1930.

He was chief counsel to the Office of the Coordinator of Inter-American Affairs from 1942 to 1945, returning to private practice in New York City from 1945 to 1961, and from 1958 to 1960 served as president of the New York City Bar Association.

[5] On October 5, 1961, Bonsal received a recess appointment from President John F. Kennedy to a new seat on the United States District Court for the Southern District of New York created by 75 Stat.

Bonsal remained in senior service until his death on July 22, 1995, in Bedford.