Oliver C. Phillips, Sr. was born in Tonganoxie, Kansas in 1873. He was the son of Charles Wesley Phillips, a Civil War veteran. Oliver Phillips Sr. was married to Blanche Phillips. His son, Oliver C. Phillips, Jr. was a professor and chair of the Classics Department at the University of Kansas. His grandsons Mark and Stephen graduated from KU and Stephen attended KU Law School. Great-grandchildren include Laura, Luke, Grace, Nick, and Tom Phillips.

Oliver C. Phillips, Sr. graduated the University of Kansas Law School in 1873 and gave the valedictory address. He was admitted to the Kansas Bar Association in the same year. Phillips practiced law in Kansas and then opened a law office in Missouri with his brother. After government service, he eventually formed a law partnership in Kansas City, Missouri.

Phillips was interested in religion and philosophy, and wrote extensive manuscripts on these subjects, though none were published. He was able to read German, French, Spanish, Italian, Latin, and ancient Greek, and was a lifelong scholar. He retired in 1963 and died in 1964.