He performed much of his field work in the western United States, investigating mineral deposits in Alaska, the Boulder Batholith in Montana, and the Gold Country of California.

Knopf was born December 2, 1882, in San Francisco, California, to German American immigrants.

[3] Knopf entered the University of California, Berkeley, where he became a student of petrology under Andrew Lawson.

The Alaskan Division, of which Knopf was one of about a dozen members, was considered the best geologic group in the USGS at that time.

Knopf's work on tin deposits in the Seward Peninsula became the basis of the dissertation for his Ph.D., which he received from Berkeley in 1909.

He encouraged students to work with the USGS as he had done; this helped mitigate the agency's brain drain following the departures.

There he accepted a visiting appointment at the Stanford University School of Earth Sciences, where he remained until his death in 1966.

[2] Knopf's field work continued through his Yale and Stanford appointments, again with a focus on western states.

He continued his work in the Boulder Batholith and investigated intrusive igneous rock bodies in the Spanish Peaks in Colorado.