Tennessee marble is a type of crystalline limestone found only in East Tennessee, in the southeastern United States. Long esteemed by architects and builders for its pinkish-gray color and the ease with which it is polished, the stone has been used in the construction of numerous notable buildings and monuments throughout the United States and Canada, including the National Gallery of Art, National Air and Space Museum, and United States Capitol in Washington, D.C., the Minnesota State Capitol, Grand Central Terminal in New York, and Union Station in Toronto. Tennessee marble achieved such popularity in the late-19th century that Knoxville, the stone's primary finishing and distribution center, became known as "The Marble City."

The Old Customs House, also called the Old Post Office, is a historic building located at the corner of Clinch Avenue and Market Street in Knoxville, Tennessee, United States. Completed in 1874, it was the city's first federal building. It housed the federal courts, excise offices and post office until 1933. From 1936 to 1976, it was used by the Tennessee Valley Authority for offices. Expanded in 2004, the building is home to the East Tennessee History Center, which includes the Lawson McGhee Library's Calvin M. McClung Historical Collection, the Knox County Archives, and the East Tennessee Historical Society's headquarters and museum. The building is listed on the National Register of Historic Places for its architectural significance.