Monroe County is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 12,376. Its county seat is Union. Monroe County was the home of Andrew Summers Rowan of Spanish–American War fame, who is immortalized in Elbert Hubbard's classic A Message to Garcia. The county was also the site of the 1928 discovery of the 34.48 carat Jones Diamond by Grover C. Jones and William "Punch" Jones. Monroe County celebrates its own holiday, Farmers' Day.