History of Marlboro County The County of Marlboro was established on March 2, 1785 and originally called Marlboro District. It was named for John Churchill, first Duke of Marlborough, whose Blenheim Palace in Oxfordshire, England, was a gift to him from Queen Anne. Marlboro District was carved from Cheraw District. Later Marlboro, Chesterfield, and Darlington Districts became Counties. When...