The assay firm of Kellogg & Humbert traces its origins to Kellogg & Co., established by John Glover Kellogg and G.F. Richter in 1853, continuing to circa June 1854, when Richter left the firm and a new partnership was formed with John Hewston, Jr., known as Kellogg & Hewston. In spring 1855, this firm was succeeded by Kellogg & Humbert, bringing together two of the best known names in the San Francisco gold business. Kellogg & Humbert were prime players in the manufacture of gold bars. On April 2, 1860, after Augustus Humbert retired, the operation continued under the name of Kellogg, Hewston & Co. Humbert sailed from San Francisco on June 5, 1860, arriving in New York City June 27. He died suddenly in June 1873 while in Paris. John Glover Kellogg remained in the gold assaying business and was active in civil affairs in San Francisco. On April 27, 1866, the firm was acquired by the San Francisco Assaying & Refining Works. Kellogg died on April 18, 1886, at the age of 62.