Apart from Maine, New Hampshire and Vermont - all Eastern seaboard states - only states boasting an overwhelming majority of white voters (ranging from 93.5% to 84.5% of the total population) were considered (since to include states with higher percentages of African-Americans and other minorities would only skew the picture due to their sizable pro-Obama vote).
Annual Household Income
Education BA degree or higher
McCain vs. Obama vote differential
The reader is invited to compare these results with those which obtained in the course of the 2012 election cycle.
Interpretation of Results
If we opt for annual household income, coupled with education, as the most reliable indicator of one's status as a member of the working class, then West Virginia wins the contest hands down as the state in which white working-class voters comprised the greatest chunk of its overall (white) population, with Kentucky, Idaho and both Dakotas close runners-up.
The Curious Case of West Virginia
There still remains to explain the rather poor (only 13.12%) pro-McCain showing in West Virginia, especially in light of the state's having scored the highest in terms of both the percentage of its white population in general and its working-class voters (as defined above) in particular: By all reasonable accounts, it should have been near the top of the list.
Not only did Trump carry the state with a staggering "68.5% of the vote.the largest share of the vote in any state" and an unprecedented 42.2% victory margin, making it only second in that category to Wyoming; duplicating what he'd done in Oklahoma, he had also won West Virginia's every county.