Unionville is a city in Putnam County, Missouri, United States.Prior to that the county seat had moved several times, often with heated debate, thus the centralized location hoping to bring "harmony" to all concerned.(see Putnam County history for more details) The Union Township trustees first met on February 4, 1873, at the court-house in Unionville.[8] On May 22, 1962, Continental Airlines Flight 11, en route from O'Hare Airport in Chicago, Illinois to the downtown Kansas City, Missouri airport, crashed in a clover field north of Unionville, near Lake Thunderhead, killing all 37 passengers and 8 crew.Investigators subsequently determined that one of the jetliner's passengers, Thomas G. Doty, detonated a bomb inside the Boeing 707 in a suicide-for-insurance plot.[10] According to the United States Census Bureau, the city has a total area of 2.00 square miles (5.18 km2), all of it land.Public education in Unionville is administered by Putnam County R-I School District.