Born on October 13, 1881, in Waynesburg, Pennsylvania, Knox received an Artium Baccalaureus degree in 1902 from Waynesburg College and after attending the University of Pennsylvania Law School, read law in 1904.

He was an Assistant United States Attorney for the Southern District of New York from 1913 to 1918.

[1] Knox was nominated by President Woodrow Wilson on March 29, 1918, to a seat on the United States District Court for the Southern District of New York vacated by Judge Martin Thomas Manton.

He was confirmed by the United States Senate on April 12, 1918, and received his commission the same day.

[1] Knox wrote two books on his judicial service, A Judge Comes of Age (1940) and Order in the Court (1943).