The above graphic depicts minimum wage adjusted for inflation (values are all given in 2017 dollars because the 2018 inflation rate isn't finalized yet). You'll notice each year a majority of states have the same minimum wage, which is the federal minimum wage. Periodic increases in minimum wage have been insufficient to keep pace with inflation, although there has been recent progress towards 1974 rates. As the federal minimum wage remained constant and inflation effectively caused a decrease in minimum wage from 1998 to 2007 and then from 2010 to present, states responded by setting their own higher minimum wages. While this is a victory for federalism, these changes are not nation-wide and tend to lag inflation. 

If you were to have asked me five years ago if a $15 minimum wage was a possibility I would have given a firm no. From the early 1980s through 2015, no state was even clearing a $10 inflation adjusted minimum wage (ignoring a handful of very progressive years for the District of Columbia).  However, beginning in 2016, states (California and Massachusetts followed by Oregon, Washington, Arizona, Connecticut, Maryland, New York, Rhode Island, and Vermont) have started clearing the $10 threshold. With the exception of city minimum wages, which can be significantly higher, a $15 minimum wage is a ways off, though it is more of a possibility now than it has been for the past 30 years. See below for still frames of particularly interesting years.

Our data set starts off towards the high end of the minimum wage spectrum with an inflation adjusted federal minimum wage of $10 (and $10.25 for Alaska). 

With a federal minimum wage of $7.25 and a handful of states with minimum wages higher than even 1974 levels, 2017 looks a lot kinder to minimum wage earners than 2006. Though inflation adjusted federal minimum wage is still significantly behind 1974 levels, there is a very reassuring trend towards darker shades of blue that I for one find promising.

Data source: Bureau of Labor Statistics, Washington Center for Equitable Growth, and the Labor Law Center