Built about 1790 as a lawyer's office at Granby on the Congaree River, this building was rolled to the new county seat called Lexington Courthouse in 1820 and was used as a medical office for Dr. Thomas Simmons (1794-1853). His widow, Mary, kept the Post Office here in 1866-67, and their daughter, Mrs. Mary S. Harth, in 1868-1894, during their tenures as postmistresses for the town. It was relocated to the Museum from the Courthouse square in 1975.