I am going to assume the original comment-or simply didn't think about inflation (common mistake...which is further understandable since the graphic doesn't make it obvious whether or not it is nominal dollars or adjusted dollars).
So in that spirit, here is another resource which talks about minimum wage and even included an adjusted minimum wage graph within:
The minimum wage is not the only measurement for this discussion, but it does seem like since the 1980's the purchasing power represented by minimum wage has been falling (but at the very least is less today than then).
> Even so, the gains for both lower- and middle-income families were outdistanced by upper-income families, whose median wealth increased by 85% over the same period, from $344,100 in 1983 to $636,000 in 2001. (Figures are expressed in 2018 dollars.)
Using this calculator which seems to be using buying power instead of actual inflation. https://www.usinflationcalculator.com/