Regarding the Dec. 13 Style article “Researcher links slaves to Castle’s sandstone”: Researcher Mark Auslander found it “likely” that the Seneca, Md., quarry that provided the red sandstone to build the Smithsonian Castle from 1847 to 1855 used slave labor for the work. He didn’t suggest that the Smithsonian directly involved slaves in its building, but he noted that some of its building contractors probably used slaves.

The researcher, the Smithsonian and other historians would benefit from direct documentary records to back up oral historical accounts and circumstantial evidence; however, if there was direct evidence for the claim, it likely burned in the Castle fire of 1865.

Given the building of the White House and the Capitol in the pre-Civil War era, none of Mr. Auslander’s findings comes as a surprise; national institutions were intertwined with slavery in thought and deed. Any suggestion that the Smithsonian has somehow avoided this aspect of the past is belied by our full cooperation with and encouragement of the research noted in the article, the work on the topic by our own renowned historians, public presentations on the Smithsonian’s history, and numerous exhibitions on slavery and its abolition.

Last week, an exhibition featuring the Emancipation Proclamation opened at the National Museum of American History. Our work on the issue of slavery will continue when we open the National Museum of African American History and Culture on the Mall in 2015.

Richard Kurin, Washington

The writer is the Smithsonian Institution’s undersecretary for history, art and culture.