Why is Douglass surprised by New Bedford in Narrative of the Life of Frederick Douglass?

New Bedford is far more wealthy and refined than Frederick Douglass had imagined, and he is astonished to discover that many of the "colored people" who lived there have "finer houses, and...(enjoy) more of the comforts of life, than the average of slaveholders in Maryland".

From having lived in the South all his life, Frederick Douglass had developed the misconception that rich people owned slaves, and that those who did not could not afford him.  This was a logical conclusion because all the rich plantation owners owned slaves, while the poor whites, who were "exceedingly poor", did not.  Douglass had somehow "imbibed the opinion that, in the absence of slaves, there could be no wealth, and very little refinement".  With this in mind, he had expected "to meet with a rough, hard-handed, and uncultivated population" upon coming to New Bedford, which, being located in the North, is a place where there is no slavery.  Douglass is awestruck when he finds himself in that city, surrounded by "ships of the finest model, in the best order, and of the largest size", and warehouses filled "to their utmost capacity", the "strongest proofs of wealth" he can imagine.

Everything about New Bedford "look(s) clean, new, and beautiful".  The people look "more able, stronger, healthier, and happier" than those he had seen in Maryland, and, in contrast to the loud and rough workingmen in Baltimore, they toiled "noiselessly", with "a sober, yet cheerful earnestness, which betokened the deep interest which (they) felt in what (they were) doing, as well as a sense of...dignity".  Douglass is ceaselessly amazed at the "amount of wealth, comfort, taste, and refinement" he finds in the Northern city.

Most astounding of all to Douglass, however, is the discovery that the "colored people" in the city, many of whom, like himself, have only recently escaped from lives of bondage, have managed to secure a standard of living for themselves that is in his eyes completely remakable.  Douglass cites the example of an acquaintance who "live(s) in a neater house; dine(s) at a better table, (takes, pays) for, and read(s) more newspapers, better under(stands) the moral religious, and political character of the nation, than nine tenths of the slaveholders in Talbot county Maryland" (Chapter 11).