John was born on October 20, 1869, in Hopkinton, Iowa. He was the son of Charles Edward and Margaret Campbell Merriam. John married Ada Gertrude Little on December 22, 1896, having three children: Lawrence Campbell, Charles Warren, and Malcolm Landers. After the death of his first wife, he married Margaret Louise Webb on February 20, 1941.
Throughout his life, he received many degrees, beginning with a BS degree from Lenox College in Iowa in 1887 and a PhD degree from the University of Munich in 1893. He also received ScD degrees from Columbia in 1921, Princeton in 1922, Yale in 1922, University of Pennsylvania in 1936, University of the State of New York in 1937, and Oregon State College in 1939, as well as LLD degrees from Wesleyan University in 1922, University of California in 1924, New York University in 1926, University of Michigan in 1933, Harvard University in 1935, George Washington University in 1937, and the University of Oregon in 1939.
John spent many years working for the University of California. From 1894 to 1899 he was an instructor of paleontology and historical geology. He became an assistant professor in 1899, an associate professor in 1905, a professor in 1912, and moved into administration as dean of faculty in 1920.
Outside of his work as a teacher, he belonged to and worked for many other associations. He was chairman of the National Research Council in 1919, president of the Carnegie Institution in Washington from 1920 to 1938 and president emeritus from 1939 until his death, a regent of the Smithsonian Institution starting in 1928, fellow of the American Association for the Advancement of Sciences and president of the Pacific Division from 1919 to 1920, president of the Geologic Society of America in 1910, president of the American Paleontology Society in 1917, president of the executive committee on the Pan American Institute of Geography and History from 1935 to 1938, and chairman of the research committee of the California State Council of Defense from 1917 to 1920. John was a member of the National Academy of Sciences in Washington, the American Philosophers Society, the Washington Academy of the Sciences, the California Academy of the Sciences, the Philadelphia Academy of Sciences, the American Academy of Arts and Sciences, American Association of University Professors, the Commission du Parc National Albert, the Christian Michelsens Institute of Bergen, Norway, the Cosmos Club of Washington, the Century Association of New York, the Commonwealth Club of California in San Francisco, corresponding member of the London Zoological Society, and honorary member of the Society of Geography and History of Michoacan, Mexico.
John was a prolific writer with over 35 major publications as well as numerous other papers on geology, paleontology, history, research, and education.
He died on October 30, 1945, in Oakland, California, after a successful life as paleontologist, educator, and administrator.
John was elected a member in the Washington Biologists’ Field Club in 1901 and awarded honorary membership in 1918.