During this fruitful time Fox also authored several books, and served as secretary of the American Astronomical Society.

After the start of World War I, Fox returned to active duty in the Army, becoming a major of infantry in France.

He ran the planetarium for eight years, also serving during this time as the first (interim) director of the Griffith Observatory in Los Angeles when it opened in 1935.

In May 1937, Fox left this job to become the director of the Chicago Museum of Science and Industry, a position he retained until 1942.

With the entry of the United States into World War II in 1941, Fox again returned to the Army, but did not perform overseas duty.