Manassas is an independent city located in the Commonwealth of Virginia. The population was 35,135 at the 2000 census. The Bureau of Economic Analysis combines the city of Manassas (along with Manassas Park) with Prince William County for statistical purposes. The City of Manassas is part of the Washington Metropolitan Area. History In 1861,the First Battle of Manassas – also widely known as the First Battle of Bull Run – the first major land battle of the American Civil War, was fo… (More on Manassas)