Mercer was born in 1924 Pine Bluff, Arkansas, where he graduated from Merrill High School and AM&N college.
Of the "six pioneers", he was the only one who did not serve in the army during World War II due to a medical condition,[3] and therefore frequently had to spend time off school to earn the money to pay for his education, serving in various jobs including teaching math at Carver High School in Marked Tree.
He also served as a special judge in several municipal and circuit courts in Arkansas's Pulaski County.
[2] He practiced law for 58 years, frequently taking cases for clients with little of no means to pay for his services.
[4] In 1957, when Little Rock Central was integrated, Mercer served as an advisor to one of the nine black students, Daisy Bates.