"It is tempting to suggest that as more white workers came to the city slaves were crowded out, but as those white workers earned money some bought slaves. Recall all the inconveniences of the city, including distances from shops to work sites where the workers lived. Slave servants walked the extra miles for their master, as well as kept house."
Quote from page 136, Slave Labor in the Capital, page 136
The want ads in the local newspapers can show us how whites regarded and used slaves and free blacks. In the first ad below, Massachusetts born William Cranch, the nephew of Abigail Adams, wanted a maid for his growing family. He offered wages and made "no objections... as to colour." Since he offered "good wages" he likely knew of free black women in the community who were house maids.
The second advertises an auction of the estate of a deceased mason named James Harrigan. I have not found him on a payroll yet so he may not have worked on the public buildings. However, I think his estate mirrors that of many other masons who were immigrants. His estate consisted of mason's tools, clothing and two slaves "accustomed to housework," a 16 year old girl and a 9 year old boy. Immigrants rarely had family to help with chores. They could easily buy slaves.
The third ad solicits quarriers for the Seneca Creek quarry. Unlike Robert Brent's ads for the Aquia Creek there is no mention of 25 or 60 slaves. Paxton and Delahunty wanted a few good men who wanted liberal wages.