Could be, but I don't hear that nearly as often as 'record high' ...
oil prices, deficits, etc. Historical records show that simply isn't true but I hear it all the time.
If you're talking about the raw number of Americans who are working, I think you could accurately say that more are working now than at any time in history. However, a more accurate measure is the unemployment (or employment) percentage rate. That rate is a good measure regardless of any growth in population.
Has the unemployment rate been lower than it is today? Certainly, including the late 1990s. Today's rate is 5.5%, about the same (5.6%) as it was in 1996 when Clinton was running for his second term. That was considered a good rate then but is somehow considered a bad rate today. Strange.