Knopf was born in New York and attended UCLA, leaving during his senior year to join the Air Force during World War II. He finished his studies at U.C. Berkeley, graduating in 1950, and began a 50-year career as a writer for motion picture and television.
He served as president of the International Writers Guild, national chairman of the WGA and president of the WGA West during 1965-67. He received 10 Writers Guild nominations and won three of them.
Knopf received the Morgan Cox Award in 1991 and the Edmund H. North Award in 2002 from WGA West.
Knopf’s credits include “Scott Joplin: King of Ragtime,” “Mrs. Sundance,” “The Girl Who Spelled Freedom,” “Baby Girl Scott,” “Peter and Paul,” and the pilot for “The Big Valley.