[1] He married Mary Isabelle (née Ost; 1906–1990) in August 1928 and moved to Sacramento to work at the California State Department of Agriculture.
After graduation, Keifer worked for the Forest Service before accepting a position as an assistant to the curator at the California Academy of Sciences, San Francisco where he mounted and labelled a backlog of material.
In a letter to Annette Braun he stated that because of the climate (fog and cool winds), San Francisco was not the ideal place for running a light or net collecting.
By then, there were eight taxonomists and over the years they handled infestations by Khapra beetle (Trogoderma granarium), pink bollworm (Pectinophora gossypiella), and carried out fruit fly surveys.
In his 39 years at the Department of Agriculture, his expertise covered all orders of insects, recording the biologies, geographical distributions and first occurrences.