Which is a service industry job that a middle-class person most likely would have had in the early 1900s? farmer bank clerk factory worker railroad worker

bank clerk

Explanation:

Farmers are not in the service industry, they're actually part of the primary sector. Construction workers are in fact part of the second sector. Railroad workers were predominantly constructors in the 1900s. So the service industry, in other words, the tertiary sector, that a middle-class person would be involved with is most likely being a bank clerk.  

deadpool

explanation: