I trust we agree that Wikipedia is a useful place to start your research and a bad place to end it. If anything I quoted is wrong, please let me know.

Yes, this country was built with slave labor. The slave owners were people of all races. This country was also built with cheap labor. The purpose of racism was to divide the working class and keep the cost of labor low by threatening white workers with the possibility of being replaced by workers of color. This is one of the reasons Marx said, "Labor in the white skin can never free itself as long as labor in the black skin is branded."