I can only answer this for the UK, others will have to give you detail on the US.

Steam locomotive drivers became viewed as viewed as an elite amongst manual workers very early in the development of railways. They needed particular skills to work cantankerous early locomotives reliably, worked away from supervision by superiors for most of the time, and were hard to replace if they were offered jobs by other railways. This led to them being paid higher wages than others in manual work. This would be around 4 times the pay of an agricultural labourer and would compare well to the pay of lower non manual workers such as bank clerks. As the Victorian era progressed engine drivers became established as an aristocracy of labour. They were literally the best paid most responsible job that someone with a basic education could aspire to. However becoming an engine driver was a lifetime career path. You would start at 14 and spend several years as an engine cleaner, then progress to being a "passed" cleaner that is trusted with occasional firing jobs. The passed means having passed tests on rules and competence. Then you would progress to fireman, then passed fireman, then engine driver. By this time you may well be in your mid30s. From there it was possible to become a locomotive inspector which was in the bottom ranks of middle class respectability. So to summarise these were the best jobs those with little formal education could aspire to, but achieving it meant hard work through the ranks, study in mutual improvement classes and night school at mechanics institutes to pass the tests and be seen as competent.