On February 23, 2020, God called upon the kind soul of Dr. O. A. Mercado. For 55 years, he practiced Podiatry and was a world-renowned foot and ankle surgeon, professor, lecturer, author, illustrator and educational video presenter. He is survived by his loving former wife, Carol. He was an outstanding father, mentor and hero to his four children; Dr. O. Kent (Kathleen), Dr. Cynthia (Matthew Ciessau), Marc (Lilly) and Matthew (Karen). He was a positive influence and loving grandfather to all of his seven grandchildren; Marc, Michelle, Daniel, Michael, Alexander, Margretta and Megan. He was the beloved uncle of Guy, Ricky, Keith and Karen. He was affectionately known as Harry by his many loyal friends. He is preceded by his parents Bernardo and Carmen Mercado. Visitation 10:00 a.m. with Mass at 11:00 a.m. on Saturday, March 7, 2020 at St. Joseph Catholic Church, 206 E. Front Street, Harvard, Illinois. Burial St. Joseph Cemetery.