It persistently fell from 83.3% in January 2008, to September 2015, where it bottomed out around 80.6%. It has been climbing since then, and is now up to 81.8%. Getting that back up near 83% would be a big win for the economy.
The highest that has ever hit, is 84.5% in 1999/2000. Healthy has historically (in the last 30 years) been anything around or above 83%. I think it's plausible the US can return to that figure in the next year.
We've struggled with the prime age unemployment due in part to the big loss in production jobs since ~2000. The continued recent (curved upward again at the end of 2016 [1]) boom in manufacturing jobs (exports are at an all-time high) should pull a lot of blue-collar workers back into the labor market. The manufacturing sector unemployment rate is incredibly low at 3.1% (lowest since June 2000, other than the 2.6% it hit before Christmas 2017).
Trump, were he wiser on macro strategy, would resolve NAFTA, close out the trade conflict with Canada & Mexico soon, come to a deal with the EU, and then focus all the trade war on China. US manufacturing will continue to boom, cheap energy and improved margins will largely ensure that. The only serious threat is some really bad trade moves with the non-China trading world.