From HuffPost: http://www.huffingtonpost.com/2009/07/08/rep-steve-king-lone-vote_n_227866.html

399-1 was the vote on acknowledging the role that Slave Labor played in the construction of the US Capitol.

The resolution:

Whereas enslaved African-Americans provided labor essential to the construction of the United States Capitol;

Whereas the report of the Architect of the Capitol entitled `History of Slave Laborers in the Construction of the United States Capitol’ documents the role of slave labor in the construction of the Capitol;

Whereas enslaved African-Americans performed the backbreaking work of quarrying the stone which comprised many of the floors, walls, and columns of the Capitol;

Whereas enslaved African-Americans also participated in other facets of construction of the Capitol, including carpentry, masonry, carting, rafting, roofing, plastering, glazing, painting, and sawing;

Whereas the marble columns in the Old Senate Chamber and the sandstone walls of the East Front corridor remain as the lasting legacies of the enslaved African-Americans who worked the quarries;

Whereas slave-quarried stones from the remnants of the original Capitol walls can be found in Rock Creek Park in the District of Columbia;

Whereas the Statue of Freedom now atop the Capitol dome could not have been cast without the pivotal intervention of Philip Reid, an enslaved African-American foundry worker who deciphered the puzzle of how to separate the 5-piece plaster model for casting when all others failed;…

and on it goes.

399-1?  Who was the one? Sreve King, R-Iowa.   King has a long history of opposing resolutions he considers frivolous; in 2007, however, he introduced a resolution “recognizing the importance of Christians and the Christian faith.”

Emphasis Mine