[benp]

If you are looking for the cities with the greatest number of NHW workers, just look for the cities with the greatest number of NHW residents. Where cheap labor exists (especially the immigrant and non-resident aliens) NHWs have moved on to other, higher paid, professions as trades and labor jobs are filled by the lowest bidders.

Years of low wage physically demanding work are required to get a foothold in the trades, many of which take years of training and apprenticeship. And even then, much of the higher wages often require overtime, the jobs may be seasonal and subject to layoffs during recessions, and by design are career limiting. Higher wages often come through business ownership or management, not in the trade itself. Careers are also often limited by the toll it takes on the body, and the loss of physical ability as one ages. And, not everyone has the capability to learn or perform the skills required in the trades. People predisposed to academic learning may not be suitable candidates for some trades. And to enter some trades "who you know" may matter. In some places, only fluent Spanish speakers may get in.

Starting wages are often at or below what one can get by working at a MacDonalds these days. Hours are not guaranteed. Some skilled trade jobs may become obsolete as technology changes.

As far as the wealthy baker example goes, looking at the BLS site for one city (Cleveland) showed the median wage for a baker to be 29k. If the baker was wealthy, it wasn't the baking that made them that way, perhaps it was business acumen, management of other bakers, or maybe marriage into wealth. Likely for many (most) other trades, the money comes when you start your own business, not from the trade itself. And not everyone will/can start their own business - that is the exception.