Born in Morgan County, Illinois, Humphrey attended Shurtleff College, and read law to enter the bar in 1880.
He was a legal clerk for the Illinois State Office of Railroad and Warehouse Commissioners from 1880 to 1883.
He was then the United States Attorney for the Southern District of Illinois from 1897 to 1901.
[1] On March 7, 1901, Humphrey was nominated by President William McKinley to a seat on the United States District Court for the Southern District of Illinois vacated by Judge William J. Allen.
Humphrey was confirmed by the United States Senate on March 8, 1901, and received his commission the same day.