The EPI article Congress has never let the federal minimum wage erode for this long by David Cooper (6/17/19) provides the graph here.
June 16th marks the longest period in history without an increase in the federal minimum wage. The last time Congress passed an increase was in May 2007, when it legislated that the minimum wage be raised to $7.25 per hour on July 24, 2009. Since the minimum wage was first established in 1938, Congress has never let it go unchanged for so long.
To get the data for this graph visit The FRED Blog The value(s) of the minimum wage. At the bottom of the page they provide direction on how to recreate the chart with FRED data. Knowing how to do this is valuable and should be incorporated into any statistics or QL course.